From: Michal Hocko <mhocko@suse.com> Memory offlining can fail just too eagerly under a heavy memory pressure. [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) [ 5410.336811] page dumped because: isolation failed [ 5410.336813] page->mem_cgroup:ffff8801cd662000 [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed Isolation has failed here because the page is not on LRU. Most probably because it was on the pcp LRU cache or it has been removed from the LRU already but it hasn't been freed yet. In both cases the page doesn't look non-migrable so retrying more makes sense. __offline_pages seems rather cluttered when it comes to the retry logic. We have 5 retries at maximum and a timeout. We could argue whether the timeout makes sense but failing just because of a race when somebody isoltes a page from LRU or puts it on a pcp LRU lists is just wrong. It only takes it to race with a process which unmaps some pages and remove them from the LRU list and we can fail the whole offline because of something that is a temporary condition and actually not harmful for the offline. Please note that unmovable pages should be already excluded during start_isolate_page_range. Fix this by removing the max retry count and only rely on the timeout resp. interruption by a signal from the userspace. Also retry rather than fail when check_pages_isolated sees some !free pages because those could be a result of the race as well. Signed-off-by: Michal Hocko <mhocko@suse.com> --- mm/memory_hotplug.c | 40 ++++++++++------------------------------ 1 file changed, 10 insertions(+), 30 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 459bbc182d10..c9dcbe6d2ac6 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1597,7 +1597,7 @@ static int __ref __offline_pages(unsigned long start_pfn, { unsigned long pfn, nr_pages, expire; long offlined_pages; - int ret, drain, retry_max, node; + int ret, node; unsigned long flags; unsigned long valid_start, valid_end; struct zone *zone; @@ -1634,43 +1634,25 @@ static int __ref __offline_pages(unsigned long start_pfn, pfn = start_pfn; expire = jiffies + timeout; - drain = 0; - retry_max = 5; repeat: /* start memory hot removal */ - ret = -EAGAIN; + ret = -EBUSY; if (time_after(jiffies, expire)) goto failed_removal; ret = -EINTR; if (signal_pending(current)) goto failed_removal; - ret = 0; - if (drain) { - lru_add_drain_all_cpuslocked(); - cond_resched(); - drain_all_pages(zone); - } + + cond_resched(); + lru_add_drain_all_cpuslocked(); + drain_all_pages(zone); pfn = scan_movable_pages(start_pfn, end_pfn); if (pfn) { /* We have movable pages */ ret = do_migrate_range(pfn, end_pfn); - if (!ret) { - drain = 1; - goto repeat; - } else { - if (ret < 0) - if (--retry_max == 0) - goto failed_removal; - yield(); - drain = 1; - goto repeat; - } + goto repeat; } - /* drain all zone's lru pagevec, this is asynchronous... */ - lru_add_drain_all_cpuslocked(); - yield(); - /* drain pcp pages, this is synchronous. */ - drain_all_pages(zone); + /* * dissolve free hugepages in the memory block before doing offlining * actually in order to make hugetlbfs's object counting consistent. @@ -1680,10 +1662,8 @@ static int __ref __offline_pages(unsigned long start_pfn, goto failed_removal; /* check again */ offlined_pages = check_pages_isolated(start_pfn, end_pfn); - if (offlined_pages < 0) { - ret = -EBUSY; - goto failed_removal; - } + if (offlined_pages < 0) + goto repeat; pr_info("Offlined Pages %ld\n", offlined_pages); /* Ok, all of our target is isolated. We cannot do rollback at this point. */ -- 2.14.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 09/04/2017 01:51 PM, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > Memory offlining can fail just too eagerly under a heavy memory pressure. > > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) > [ 5410.336811] page dumped because: isolation failed > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed > > Isolation has failed here because the page is not on LRU. Most probably > because it was on the pcp LRU cache or it has been removed from the LRU > already but it hasn't been freed yet. In both cases the page doesn't look > non-migrable so retrying more makes sense. > > __offline_pages seems rather cluttered when it comes to the retry > logic. We have 5 retries at maximum and a timeout. We could argue > whether the timeout makes sense but failing just because of a race when > somebody isoltes a page from LRU or puts it on a pcp LRU lists is just > wrong. It only takes it to race with a process which unmaps some pages > and remove them from the LRU list and we can fail the whole offline > because of something that is a temporary condition and actually not > harmful for the offline. Please note that unmovable pages should be > already excluded during start_isolate_page_range. > > Fix this by removing the max retry count and only rely on the timeout > resp. interruption by a signal from the userspace. Also retry rather > than fail when check_pages_isolated sees some !free pages because those > could be a result of the race as well. > > Signed-off-by: Michal Hocko <mhocko@suse.com> > --- > mm/memory_hotplug.c | 40 ++++++++++------------------------------ > 1 file changed, 10 insertions(+), 30 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 459bbc182d10..c9dcbe6d2ac6 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1597,7 +1597,7 @@ static int __ref __offline_pages(unsigned long start_pfn, > { > unsigned long pfn, nr_pages, expire; > long offlined_pages; > - int ret, drain, retry_max, node; > + int ret, node; > unsigned long flags; > unsigned long valid_start, valid_end; > struct zone *zone; > @@ -1634,43 +1634,25 @@ static int __ref __offline_pages(unsigned long start_pfn, > > pfn = start_pfn; > expire = jiffies + timeout; > - drain = 0; > - retry_max = 5; > repeat: > /* start memory hot removal */ > - ret = -EAGAIN; > + ret = -EBUSY; > if (time_after(jiffies, expire)) > goto failed_removal; > ret = -EINTR; > if (signal_pending(current)) > goto failed_removal; > - ret = 0; > - if (drain) { > - lru_add_drain_all_cpuslocked(); > - cond_resched(); > - drain_all_pages(zone); > - } Why we had this condition before that only when we fail in migration later in do_migrate_range function, drain the lru lists in the next attempt. Why not from the first attempt itself ? Just being curious. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Tue 05-09-17 11:59:36, Anshuman Khandual wrote: [...] > > @@ -1634,43 +1634,25 @@ static int __ref __offline_pages(unsigned long start_pfn, > > > > pfn = start_pfn; > > expire = jiffies + timeout; > > - drain = 0; > > - retry_max = 5; > > repeat: > > /* start memory hot removal */ > > - ret = -EAGAIN; > > + ret = -EBUSY; > > if (time_after(jiffies, expire)) > > goto failed_removal; > > ret = -EINTR; > > if (signal_pending(current)) > > goto failed_removal; > > - ret = 0; > > - if (drain) { > > - lru_add_drain_all_cpuslocked(); > > - cond_resched(); > > - drain_all_pages(zone); > > - } > > Why we had this condition before that only when we fail in migration > later in do_migrate_range function, drain the lru lists in the next > attempt. Why not from the first attempt itself ? Just being curious. I can only guess but draining used to invoke IPIs and that is really costly so an optimistic attempt could try without draining and do that only if the migration fails. Now that we have it all done in WQ context there shouldn't be any reason to optimize for draining. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 09/04/2017 10:21 AM, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > Memory offlining can fail just too eagerly under a heavy memory pressure. > > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) > [ 5410.336811] page dumped because: isolation failed > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed > > Isolation has failed here because the page is not on LRU. Most probably > because it was on the pcp LRU cache or it has been removed from the LRU > already but it hasn't been freed yet. In both cases the page doesn't look > non-migrable so retrying more makes sense. > > __offline_pages seems rather cluttered when it comes to the retry > logic. We have 5 retries at maximum and a timeout. We could argue > whether the timeout makes sense but failing just because of a race when > somebody isoltes a page from LRU or puts it on a pcp LRU lists is just > wrong. It only takes it to race with a process which unmaps some pages > and remove them from the LRU list and we can fail the whole offline > because of something that is a temporary condition and actually not > harmful for the offline. Please note that unmovable pages should be > already excluded during start_isolate_page_range. Hmm, the has_unmovable_pages() check doesn't offer any strict guarantees due to races, per its comment. Also at the very quick glance, I see a check where it assumes that MIGRATE_MOVABLE pageblock will have no unmovable pages. There is no such guarantee even without races. > Fix this by removing the max retry count and only rely on the timeout > resp. interruption by a signal from the userspace. Also retry rather > than fail when check_pages_isolated sees some !free pages because those > could be a result of the race as well. > > Signed-off-by: Michal Hocko <mhocko@suse.com> Even within a movable node where has_unmovable_pages() is a non-issue, you could have pinned movable pages where the pinning is not temporary. So after this patch, this will really keep retrying forever. I'm not saying it's wrong, just pointing it out, since the changelog seems to assume there would be only temporary failures possible and thus unbound retries are always correct. The obvious problem if we wanted to avoid this, is how to recognize non-temporary failures... > --- > mm/memory_hotplug.c | 40 ++++++++++------------------------------ > 1 file changed, 10 insertions(+), 30 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 459bbc182d10..c9dcbe6d2ac6 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1597,7 +1597,7 @@ static int __ref __offline_pages(unsigned long start_pfn, > { > unsigned long pfn, nr_pages, expire; > long offlined_pages; > - int ret, drain, retry_max, node; > + int ret, node; > unsigned long flags; > unsigned long valid_start, valid_end; > struct zone *zone; > @@ -1634,43 +1634,25 @@ static int __ref __offline_pages(unsigned long start_pfn, > > pfn = start_pfn; > expire = jiffies + timeout; > - drain = 0; > - retry_max = 5; > repeat: > /* start memory hot removal */ > - ret = -EAGAIN; > + ret = -EBUSY; > if (time_after(jiffies, expire)) > goto failed_removal; > ret = -EINTR; > if (signal_pending(current)) > goto failed_removal; > - ret = 0; > - if (drain) { > - lru_add_drain_all_cpuslocked(); > - cond_resched(); > - drain_all_pages(zone); > - } > + > + cond_resched(); > + lru_add_drain_all_cpuslocked(); > + drain_all_pages(zone); > > pfn = scan_movable_pages(start_pfn, end_pfn); > if (pfn) { /* We have movable pages */ > ret = do_migrate_range(pfn, end_pfn); > - if (!ret) { > - drain = 1; > - goto repeat; > - } else { > - if (ret < 0) > - if (--retry_max == 0) > - goto failed_removal; > - yield(); > - drain = 1; > - goto repeat; > - } > + goto repeat; > } > - /* drain all zone's lru pagevec, this is asynchronous... */ > - lru_add_drain_all_cpuslocked(); > - yield(); > - /* drain pcp pages, this is synchronous. */ > - drain_all_pages(zone); > + > /* > * dissolve free hugepages in the memory block before doing offlining > * actually in order to make hugetlbfs's object counting consistent. > @@ -1680,10 +1662,8 @@ static int __ref __offline_pages(unsigned long start_pfn, > goto failed_removal; > /* check again */ > offlined_pages = check_pages_isolated(start_pfn, end_pfn); > - if (offlined_pages < 0) { > - ret = -EBUSY; > - goto failed_removal; > - } > + if (offlined_pages < 0) > + goto repeat; > pr_info("Offlined Pages %ld\n", offlined_pages); > /* Ok, all of our target is isolated. > We cannot do rollback at this point. */ > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Fri 08-09-17 19:26:06, Vlastimil Babka wrote: > On 09/04/2017 10:21 AM, Michal Hocko wrote: > > From: Michal Hocko <mhocko@suse.com> > > > > Memory offlining can fail just too eagerly under a heavy memory pressure. > > > > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 > > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) > > [ 5410.336811] page dumped because: isolation failed > > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 > > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed > > > > Isolation has failed here because the page is not on LRU. Most probably > > because it was on the pcp LRU cache or it has been removed from the LRU > > already but it hasn't been freed yet. In both cases the page doesn't look > > non-migrable so retrying more makes sense. > > > > __offline_pages seems rather cluttered when it comes to the retry > > logic. We have 5 retries at maximum and a timeout. We could argue > > whether the timeout makes sense but failing just because of a race when > > somebody isoltes a page from LRU or puts it on a pcp LRU lists is just > > wrong. It only takes it to race with a process which unmaps some pages > > and remove them from the LRU list and we can fail the whole offline > > because of something that is a temporary condition and actually not > > harmful for the offline. Please note that unmovable pages should be > > already excluded during start_isolate_page_range. > > Hmm, the has_unmovable_pages() check doesn't offer any strict guarantees due to > races, per its comment. Also at the very quick glance, I see a check where it > assumes that MIGRATE_MOVABLE pageblock will have no unmovable pages. There is no > such guarantee even without races. Yes, you are right that there are races possible but practically speaking non-movable memblocks (in !MOVABLE_ZONE) would be very likely to have reliably unmovable pages and so has_unmovable_pages would bail out. And ZONE_MOVABLE memblocks with permanently pinned pages sound like a bug to me. > > Fix this by removing the max retry count and only rely on the timeout > > resp. interruption by a signal from the userspace. Also retry rather > > than fail when check_pages_isolated sees some !free pages because those > > could be a result of the race as well. > > > > Signed-off-by: Michal Hocko <mhocko@suse.com> > > Even within a movable node where has_unmovable_pages() is a non-issue, you could > have pinned movable pages where the pinning is not temporary. Who would pin those pages? Such a page would be unreclaimable as well and thus a memory leak and I would argue it would be a bug. > So after this > patch, this will really keep retrying forever. I'm not saying it's wrong, just > pointing it out, since the changelog seems to assume there would be only > temporary failures possible and thus unbound retries are always correct. > The obvious problem if we wanted to avoid this, is how to recognize > non-temporary failures... Yes, we should be able to distinguish the two and hopefully we can teach the migration code to distinguish between EBUSY (likely permanent) and EGAIN (temporal) failure. This sound like something we should aim for longterm I guess. Anyway as I've said in other email. If somebody really wants to have a guaratee of a bounded retry then it is trivial to set up an alarm and send a signal itself to bail out. Do you think that the changelog should be more clear about this? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 09/11/2017 10:17 AM, Michal Hocko wrote: > On Fri 08-09-17 19:26:06, Vlastimil Babka wrote: >> On 09/04/2017 10:21 AM, Michal Hocko wrote: >>> From: Michal Hocko <mhocko@suse.com> >>> >>> Fix this by removing the max retry count and only rely on the timeout >>> resp. interruption by a signal from the userspace. Also retry rather >>> than fail when check_pages_isolated sees some !free pages because those >>> could be a result of the race as well. >>> >>> Signed-off-by: Michal Hocko <mhocko@suse.com> >> >> Even within a movable node where has_unmovable_pages() is a non-issue, you could >> have pinned movable pages where the pinning is not temporary. > > Who would pin those pages? Such a page would be unreclaimable as well > and thus a memory leak and I would argue it would be a bug. I don't know who exactly, but generally it's a problem for CMA and a reason why there was some effort from PeterZ to introduce an API for long-term pinning. >> So after this >> patch, this will really keep retrying forever. I'm not saying it's wrong, just >> pointing it out, since the changelog seems to assume there would be only >> temporary failures possible and thus unbound retries are always correct. >> The obvious problem if we wanted to avoid this, is how to recognize >> non-temporary failures... > > Yes, we should be able to distinguish the two and hopefully we can teach > the migration code to distinguish between EBUSY (likely permanent) and > EGAIN (temporal) failure. This sound like something we should aim for > longterm I guess. Anyway as I've said in other email. If somebody really > wants to have a guaratee of a bounded retry then it is trivial to set up > an alarm and send a signal itself to bail out. Sure, I would just be careful about not breaking existing userspace (udev?) when offline triggered via ACPI from some management interface (or whatever the exact mechanism is). > Do you think that the changelog should be more clear about this? It certainly wouldn't hurt :) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Wed 13-09-17 13:41:20, Vlastimil Babka wrote: > On 09/11/2017 10:17 AM, Michal Hocko wrote: [...] > > Yes, we should be able to distinguish the two and hopefully we can teach > > the migration code to distinguish between EBUSY (likely permanent) and > > EGAIN (temporal) failure. This sound like something we should aim for > > longterm I guess. Anyway as I've said in other email. If somebody really > > wants to have a guaratee of a bounded retry then it is trivial to set up > > an alarm and send a signal itself to bail out. > > Sure, I would just be careful about not breaking existing userspace > (udev?) when offline triggered via ACPI from some management interface > (or whatever the exact mechanism is). The thing is that there is absolutely no timing guarantee even with retry limit in place. We are doing allocations, potentially bouncing on locks which can be taken elsewhere etc... So if somebody really depend on this then it is pretty much broken already. > > Do you think that the changelog should be more clear about this? > > It certainly wouldn't hurt :) So what do you think about the following wording: commit 23c4ded55c2ba880165a9f5b8a67694361fb6bc7 Author: Michal Hocko <mhocko@suse.com> Date: Mon Aug 28 13:13:06 2017 +0200 mm, memory_hotplug: remove timeout from __offline_memory We have a hardcoded 120s timeout after which the memory offline fails basically since the hot remove has been introduced. This is essentially a policy implemented in the kernel. Moreover there is no way to adjust the timeout and so we are sometimes facing memory offline failures if the system is under a heavy memory pressure or very intensive CPU workload on large machines. It is not very clear what purpose the timeout actually serves. The offline operation is interruptible by a signal so if userspace wants some timeout based termination this can be done trivially by sending a signal. If there is a strong usecase to do this from the kernel then we should do it properly and have a it tunable from the userspace with the timeout disabled by default along with the explanation who uses it and for what purporse. Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Michal Hocko <mhocko@suse.com> -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Wed 13-09-17 14:10:01, Michal Hocko wrote:
> On Wed 13-09-17 13:41:20, Vlastimil Babka wrote:
> > On 09/11/2017 10:17 AM, Michal Hocko wrote:
> [...]
> > > Yes, we should be able to distinguish the two and hopefully we can teach
> > > the migration code to distinguish between EBUSY (likely permanent) and
> > > EGAIN (temporal) failure. This sound like something we should aim for
> > > longterm I guess. Anyway as I've said in other email. If somebody really
> > > wants to have a guaratee of a bounded retry then it is trivial to set up
> > > an alarm and send a signal itself to bail out.
> >
> > Sure, I would just be careful about not breaking existing userspace
> > (udev?) when offline triggered via ACPI from some management interface
> > (or whatever the exact mechanism is).
>
> The thing is that there is absolutely no timing guarantee even with
> retry limit in place. We are doing allocations, potentially bouncing on
> locks which can be taken elsewhere etc... So if somebody really depend
> on this then it is pretty much broken already.
>
> > > Do you think that the changelog should be more clear about this?
> >
> > It certainly wouldn't hurt :)
>
> So what do you think about the following wording:
Ups, wrong patch
On 09/13/2017 02:14 PM, Michal Hocko wrote: >>>> Do you think that the changelog should be more clear about this? >>> >>> It certainly wouldn't hurt :) >> >> So what do you think about the following wording: > > Ups, wrong patch > > > From 8639496a834b4a7c24972ec23b17e50f0d6a304c Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@suse.com> > Date: Mon, 14 Aug 2017 10:46:12 +0200 > Subject: [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early > > Memory offlining can fail just too eagerly under a heavy memory pressure. > > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) > [ 5410.336811] page dumped because: isolation failed > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed > > Isolation has failed here because the page is not on LRU. Most probably > because it was on the pcp LRU cache or it has been removed from the LRU > already but it hasn't been freed yet. In both cases the page doesn't look > non-migrable so retrying more makes sense. > > __offline_pages seems rather cluttered when it comes to the retry > logic. We have 5 retries at maximum and a timeout. We could argue > whether the timeout makes sense but failing just because of a race when > somebody isoltes a page from LRU or puts it on a pcp LRU lists is just > wrong. It only takes it to race with a process which unmaps some pages > and remove them from the LRU list and we can fail the whole offline > because of something that is a temporary condition and actually not > harmful for the offline. > > Please note that unmovable pages should be already excluded during > start_isolate_page_range. We could argue that has_unmovable_pages is > racy and MIGRATE_MOVABLE check doesn't provide any hard guarantee either > but kernel zones (aka < ZONE_MOVABLE) will very likely detect unmovable > pages in most cases and movable zone shouldn't contain unmovable pages > at all. Some of those pages might be pinned but not for ever because > that would be a bug on its own. In any case the context is still > interruptible and so the userspace can easily bail out when the > operation takes too long. This is certainly better behavior than a > hardcoded retry loop which is racy. > > Fix this by removing the max retry count and only rely on the timeout > resp. interruption by a signal from the userspace. Also retry rather > than fail when check_pages_isolated sees some !free pages because those > could be a result of the race as well. > > Signed-off-by: Michal Hocko <mhocko@suse.com> Yeah, that's better, thanks. Acked-by: Vlastimil Babka <vbabka@suse.cz> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Wed 13-09-17 14:19:19, Vlastimil Babka wrote: > On 09/13/2017 02:14 PM, Michal Hocko wrote: > >>>> Do you think that the changelog should be more clear about this? > >>> > >>> It certainly wouldn't hurt :) > >> > >> So what do you think about the following wording: > > > > Ups, wrong patch > > > > > > From 8639496a834b4a7c24972ec23b17e50f0d6a304c Mon Sep 17 00:00:00 2001 > > From: Michal Hocko <mhocko@suse.com> > > Date: Mon, 14 Aug 2017 10:46:12 +0200 > > Subject: [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early > > > > Memory offlining can fail just too eagerly under a heavy memory pressure. > > > > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 > > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) > > [ 5410.336811] page dumped because: isolation failed > > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 > > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed > > > > Isolation has failed here because the page is not on LRU. Most probably > > because it was on the pcp LRU cache or it has been removed from the LRU > > already but it hasn't been freed yet. In both cases the page doesn't look > > non-migrable so retrying more makes sense. > > > > __offline_pages seems rather cluttered when it comes to the retry > > logic. We have 5 retries at maximum and a timeout. We could argue > > whether the timeout makes sense but failing just because of a race when > > somebody isoltes a page from LRU or puts it on a pcp LRU lists is just > > wrong. It only takes it to race with a process which unmaps some pages > > and remove them from the LRU list and we can fail the whole offline > > because of something that is a temporary condition and actually not > > harmful for the offline. > > > > Please note that unmovable pages should be already excluded during > > start_isolate_page_range. We could argue that has_unmovable_pages is > > racy and MIGRATE_MOVABLE check doesn't provide any hard guarantee either > > but kernel zones (aka < ZONE_MOVABLE) will very likely detect unmovable > > pages in most cases and movable zone shouldn't contain unmovable pages > > at all. Some of those pages might be pinned but not for ever because > > that would be a bug on its own. In any case the context is still > > interruptible and so the userspace can easily bail out when the > > operation takes too long. This is certainly better behavior than a > > hardcoded retry loop which is racy. > > > > Fix this by removing the max retry count and only rely on the timeout > > resp. interruption by a signal from the userspace. Also retry rather > > than fail when check_pages_isolated sees some !free pages because those > > could be a result of the race as well. > > > > Signed-off-by: Michal Hocko <mhocko@suse.com> > > Yeah, that's better, thanks. > > Acked-by: Vlastimil Babka <vbabka@suse.cz> Thanks. I will give it a day and repost the series. If somebody still have some concerns please speak up. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
Hi, this has been previously sent http://lkml.kernel.org/r/20170904082148.23131-1-mhocko@kernel.org No fundamental objections have been raised. There were some questions about potential permanent migration failures but those are deemed unlikely and not really problematic because the context is interruptible. I have tried to clarify the wording to be more clear. original changelog: While testing memory hotplug on a large 4TB machine we have noticed that memory offlining is just too eager to fail. The primary reason is that the retry logic is just too easy to give up. We have 4 ways out of the offline - we have a permanent failure (isolation or memory notifiers fail, or hugetlb pages cannot be dropped) - userspace sends a signal - a hardcoded 120s timeout expires - page migration fails 5 times This is way too convoluted and it doesn't scale very well. We have seen both temporary migration failures as well as 120s being triggered. After removing those restrictions we were able to pass stress testing during memory hot remove without any other negative side effects observed. Therefore I suggest dropping both hard coded policies. I couldn't have found any specific reason for them in the changelog. I neither didn't get any response [1] from Kamezawa. If we need some upper bound - e.g. timeout based - then we should have a proper and user defined policy for that. In any case there should be a clear use case when introducing it. Any comments, objections? Shortlog Michal Hocko (2): mm, memory_hotplug: do not fail offlining too early mm, memory_hotplug: remove timeout from __offline_memory Diffstat mm/memory_hotplug.c | 48 ++++++++++++------------------------------------ 1 file changed, 12 insertions(+), 36 deletions(-) [1] http://lkml.kernel.org/r/20170828094316.GF17097@dhcp22.suse.cz -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
From: Michal Hocko <mhocko@suse.com> Memory offlining can fail just too eagerly under a heavy memory pressure. [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) [ 5410.336811] page dumped because: isolation failed [ 5410.336813] page->mem_cgroup:ffff8801cd662000 [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed Isolation has failed here because the page is not on LRU. Most probably because it was on the pcp LRU cache or it has been removed from the LRU already but it hasn't been freed yet. In both cases the page doesn't look non-migrable so retrying more makes sense. __offline_pages seems rather cluttered when it comes to the retry logic. We have 5 retries at maximum and a timeout. We could argue whether the timeout makes sense but failing just because of a race when somebody isoltes a page from LRU or puts it on a pcp LRU lists is just wrong. It only takes it to race with a process which unmaps some pages and remove them from the LRU list and we can fail the whole offline because of something that is a temporary condition and actually not harmful for the offline. Please note that unmovable pages should be already excluded during start_isolate_page_range. We could argue that has_unmovable_pages is racy and MIGRATE_MOVABLE check doesn't provide any hard guarantee either but kernel zones (aka < ZONE_MOVABLE) will very likely detect unmovable pages in most cases and movable zone shouldn't contain unmovable pages at all. Some of those pages might be pinned but not for ever because that would be a bug on its own. In any case the context is still interruptible and so the userspace can easily bail out when the operation takes too long. This is certainly better behavior than a hardcoded retry loop which is racy. Fix this by removing the max retry count and only rely on the timeout resp. interruption by a signal from the userspace. Also retry rather than fail when check_pages_isolated sees some !free pages because those could be a result of the race as well. Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Michal Hocko <mhocko@suse.com> --- mm/memory_hotplug.c | 40 ++++++++++------------------------------ 1 file changed, 10 insertions(+), 30 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 459bbc182d10..c9dcbe6d2ac6 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1597,7 +1597,7 @@ static int __ref __offline_pages(unsigned long start_pfn, { unsigned long pfn, nr_pages, expire; long offlined_pages; - int ret, drain, retry_max, node; + int ret, node; unsigned long flags; unsigned long valid_start, valid_end; struct zone *zone; @@ -1634,43 +1634,25 @@ static int __ref __offline_pages(unsigned long start_pfn, pfn = start_pfn; expire = jiffies + timeout; - drain = 0; - retry_max = 5; repeat: /* start memory hot removal */ - ret = -EAGAIN; + ret = -EBUSY; if (time_after(jiffies, expire)) goto failed_removal; ret = -EINTR; if (signal_pending(current)) goto failed_removal; - ret = 0; - if (drain) { - lru_add_drain_all_cpuslocked(); - cond_resched(); - drain_all_pages(zone); - } + + cond_resched(); + lru_add_drain_all_cpuslocked(); + drain_all_pages(zone); pfn = scan_movable_pages(start_pfn, end_pfn); if (pfn) { /* We have movable pages */ ret = do_migrate_range(pfn, end_pfn); - if (!ret) { - drain = 1; - goto repeat; - } else { - if (ret < 0) - if (--retry_max == 0) - goto failed_removal; - yield(); - drain = 1; - goto repeat; - } + goto repeat; } - /* drain all zone's lru pagevec, this is asynchronous... */ - lru_add_drain_all_cpuslocked(); - yield(); - /* drain pcp pages, this is synchronous. */ - drain_all_pages(zone); + /* * dissolve free hugepages in the memory block before doing offlining * actually in order to make hugetlbfs's object counting consistent. @@ -1680,10 +1662,8 @@ static int __ref __offline_pages(unsigned long start_pfn, goto failed_removal; /* check again */ offlined_pages = check_pages_isolated(start_pfn, end_pfn); - if (offlined_pages < 0) { - ret = -EBUSY; - goto failed_removal; - } + if (offlined_pages < 0) + goto repeat; pr_info("Offlined Pages %ld\n", offlined_pages); /* Ok, all of our target is isolated. We cannot do rollback at this point. */ -- 2.14.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
From: Michal Hocko <mhocko@suse.com> We have a hardcoded 120s timeout after which the memory offline fails basically since the hot remove has been introduced. This is essentially a policy implemented in the kernel. Moreover there is no way to adjust the timeout and so we are sometimes facing memory offline failures if the system is under a heavy memory pressure or very intensive CPU workload on large machines. It is not very clear what purpose the timeout actually serves. The offline operation is interruptible by a signal so if userspace wants some timeout based termination this can be done trivially by sending a signal. If there is a strong usecase to do this from the kernel then we should do it properly and have a it tunable from the userspace with the timeout disabled by default along with the explanation who uses it and for what purporse. Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Michal Hocko <mhocko@suse.com> --- mm/memory_hotplug.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index c9dcbe6d2ac6..b8a85c11360e 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1593,9 +1593,9 @@ static void node_states_clear_node(int node, struct memory_notify *arg) } static int __ref __offline_pages(unsigned long start_pfn, - unsigned long end_pfn, unsigned long timeout) + unsigned long end_pfn) { - unsigned long pfn, nr_pages, expire; + unsigned long pfn, nr_pages; long offlined_pages; int ret, node; unsigned long flags; @@ -1633,12 +1633,8 @@ static int __ref __offline_pages(unsigned long start_pfn, goto failed_removal; pfn = start_pfn; - expire = jiffies + timeout; repeat: /* start memory hot removal */ - ret = -EBUSY; - if (time_after(jiffies, expire)) - goto failed_removal; ret = -EINTR; if (signal_pending(current)) goto failed_removal; @@ -1711,7 +1707,7 @@ static int __ref __offline_pages(unsigned long start_pfn, /* Must be protected by mem_hotplug_begin() or a device_lock */ int offline_pages(unsigned long start_pfn, unsigned long nr_pages) { - return __offline_pages(start_pfn, start_pfn + nr_pages, 120 * HZ); + return __offline_pages(start_pfn, start_pfn + nr_pages); } #endif /* CONFIG_MEMORY_HOTREMOVE */ -- 2.14.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
Michal Hocko <mhocko@kernel.org> writes: > From: Michal Hocko <mhocko@suse.com> > > Memory offlining can fail just too eagerly under a heavy memory pressure. > > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) > [ 5410.336811] page dumped because: isolation failed > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed > > Isolation has failed here because the page is not on LRU. Most probably > because it was on the pcp LRU cache or it has been removed from the LRU > already but it hasn't been freed yet. In both cases the page doesn't look > non-migrable so retrying more makes sense. This breaks offline for me. Prior to this commit: /sys/devices/system/memory/memory0# time echo 0 > online -bash: echo: write error: Device or resource busy real 0m0.001s user 0m0.000s sys 0m0.001s After: /sys/devices/system/memory/memory0# time echo 0 > online -bash: echo: write error: Device or resource busy real 2m0.009s user 0m0.000s sys 1m25.035s There's no way that block can be removed, it contains the kernel text, so it should instantly fail - which it used to. With commit 3aa2823fdf66 ("mm, memory_hotplug: remove timeout from __offline_memory") also applied, it appears to just get stuck forever, and I get lots of: [ 1232.112953] INFO: task kworker/3:0:4609 blocked for more than 120 seconds. [ 1232.113067] Not tainted 4.14.0-rc4-gcc6-next-20171009-g49827b9 #1 [ 1232.113183] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 1232.113319] kworker/3:0 D11984 4609 2 0x00000800 [ 1232.113416] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func [ 1232.113531] Call Trace: [ 1232.113579] [c0000000fb2db7a0] [c0000000fb2db900] 0xc0000000fb2db900 (unreliable) [ 1232.113717] [c0000000fb2db970] [c00000000001c964] __switch_to+0x304/0x6e0 [ 1232.113840] [c0000000fb2dba10] [c000000000a408c0] __schedule+0x2e0/0xa80 [ 1232.113978] [c0000000fb2dbae0] [c000000000a410a8] schedule+0x48/0xc0 [ 1232.114113] [c0000000fb2dbb10] [c000000000a44d88] rwsem_down_read_failed+0x128/0x1b0 [ 1232.114269] [c0000000fb2dbb70] [c0000000001696a8] __percpu_down_read+0x108/0x110 [ 1232.114426] [c0000000fb2dbba0] [c00000000032e498] get_online_mems+0x68/0x80 [ 1232.115487] [c0000000fb2dbbc0] [c0000000002c82ec] memcg_create_kmem_cache+0x4c/0x190 [ 1232.115651] [c0000000fb2dbc60] [c0000000003483b8] memcg_kmem_cache_create_func+0x38/0xf0 [ 1232.115809] [c0000000fb2dbc90] [c000000000121594] process_one_work+0x2b4/0x590 [ 1232.115964] [c0000000fb2dbd20] [c000000000121908] worker_thread+0x98/0x5d0 [ 1232.116095] [c0000000fb2dbdc0] [c00000000012a134] kthread+0x164/0x1b0 [ 1232.116229] [c0000000fb2dbe30] [c00000000000bae0] ret_from_kernel_thread+0x5c/0x7c cheers -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Tue 10-10-17 23:05:08, Michael Ellerman wrote: > Michal Hocko <mhocko@kernel.org> writes: > > > From: Michal Hocko <mhocko@suse.com> > > > > Memory offlining can fail just too eagerly under a heavy memory pressure. > > > > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 > > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) > > [ 5410.336811] page dumped because: isolation failed > > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 > > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed > > > > Isolation has failed here because the page is not on LRU. Most probably > > because it was on the pcp LRU cache or it has been removed from the LRU > > already but it hasn't been freed yet. In both cases the page doesn't look > > non-migrable so retrying more makes sense. > > This breaks offline for me. > > Prior to this commit: > /sys/devices/system/memory/memory0# time echo 0 > online > -bash: echo: write error: Device or resource busy > > real 0m0.001s > user 0m0.000s > sys 0m0.001s > > After: > /sys/devices/system/memory/memory0# time echo 0 > online > -bash: echo: write error: Device or resource busy > > real 2m0.009s > user 0m0.000s > sys 1m25.035s > > > There's no way that block can be removed, it contains the kernel text, > so it should instantly fail - which it used to. OK, that means that start_isolate_page_range should have failed but it hasn't for some reason. I strongly suspect has_unmovable_pages is doing something wrong. Is the kernel text marked somehow? E.g. PageReserved? In other words, does the diff below helps? diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3badcedf96a7..00d042052501 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7368,6 +7368,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, page = pfn_to_page(check); + if (PageReserved(page)) + return true; + /* * Hugepages are not in LRU lists, but they're movable. * We need not scan over tail pages bacause we don't > With commit 3aa2823fdf66 ("mm, memory_hotplug: remove timeout from > __offline_memory") also applied, it appears to just get stuck forever, > and I get lots of: > > [ 1232.112953] INFO: task kworker/3:0:4609 blocked for more than 120 seconds. > [ 1232.113067] Not tainted 4.14.0-rc4-gcc6-next-20171009-g49827b9 #1 > [ 1232.113183] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 1232.113319] kworker/3:0 D11984 4609 2 0x00000800 > [ 1232.113416] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func > [ 1232.113531] Call Trace: > [ 1232.113579] [c0000000fb2db7a0] [c0000000fb2db900] 0xc0000000fb2db900 (unreliable) > [ 1232.113717] [c0000000fb2db970] [c00000000001c964] __switch_to+0x304/0x6e0 > [ 1232.113840] [c0000000fb2dba10] [c000000000a408c0] __schedule+0x2e0/0xa80 > [ 1232.113978] [c0000000fb2dbae0] [c000000000a410a8] schedule+0x48/0xc0 > [ 1232.114113] [c0000000fb2dbb10] [c000000000a44d88] rwsem_down_read_failed+0x128/0x1b0 > [ 1232.114269] [c0000000fb2dbb70] [c0000000001696a8] __percpu_down_read+0x108/0x110 > [ 1232.114426] [c0000000fb2dbba0] [c00000000032e498] get_online_mems+0x68/0x80 > [ 1232.115487] [c0000000fb2dbbc0] [c0000000002c82ec] memcg_create_kmem_cache+0x4c/0x190 > [ 1232.115651] [c0000000fb2dbc60] [c0000000003483b8] memcg_kmem_cache_create_func+0x38/0xf0 > [ 1232.115809] [c0000000fb2dbc90] [c000000000121594] process_one_work+0x2b4/0x590 > [ 1232.115964] [c0000000fb2dbd20] [c000000000121908] worker_thread+0x98/0x5d0 > [ 1232.116095] [c0000000fb2dbdc0] [c00000000012a134] kthread+0x164/0x1b0 > [ 1232.116229] [c0000000fb2dbe30] [c00000000000bae0] ret_from_kernel_thread+0x5c/0x7c I do not see how this is related to the offline path. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
Michal Hocko <mhocko@kernel.org> writes: > On Tue 10-10-17 23:05:08, Michael Ellerman wrote: >> Michal Hocko <mhocko@kernel.org> writes: >> >> > From: Michal Hocko <mhocko@suse.com> >> > >> > Memory offlining can fail just too eagerly under a heavy memory pressure. >> > >> > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 >> > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) >> > [ 5410.336811] page dumped because: isolation failed >> > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 >> > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed >> > >> > Isolation has failed here because the page is not on LRU. Most probably >> > because it was on the pcp LRU cache or it has been removed from the LRU >> > already but it hasn't been freed yet. In both cases the page doesn't look >> > non-migrable so retrying more makes sense. >> >> This breaks offline for me. >> >> Prior to this commit: >> /sys/devices/system/memory/memory0# time echo 0 > online >> -bash: echo: write error: Device or resource busy >> >> real 0m0.001s >> user 0m0.000s >> sys 0m0.001s >> >> After: >> /sys/devices/system/memory/memory0# time echo 0 > online >> -bash: echo: write error: Device or resource busy >> >> real 2m0.009s >> user 0m0.000s >> sys 1m25.035s >> >> >> There's no way that block can be removed, it contains the kernel text, >> so it should instantly fail - which it used to. > > OK, that means that start_isolate_page_range should have failed but it > hasn't for some reason. I strongly suspect has_unmovable_pages is doing > something wrong. Is the kernel text marked somehow? E.g. PageReserved? I'm not sure how the text is marked, will have to dig into that. > In other words, does the diff below helps? No that doesn't help. > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3badcedf96a7..00d042052501 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7368,6 +7368,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > > page = pfn_to_page(check); > > + if (PageReserved(page)) > + return true; > + > /* > * Hugepages are not in LRU lists, but they're movable. > * We need not scan over tail pages bacause we don't > > >> With commit 3aa2823fdf66 ("mm, memory_hotplug: remove timeout from >> __offline_memory") also applied, it appears to just get stuck forever, >> and I get lots of: >> >> [ 1232.112953] INFO: task kworker/3:0:4609 blocked for more than 120 seconds. >> [ 1232.113067] Not tainted 4.14.0-rc4-gcc6-next-20171009-g49827b9 #1 >> [ 1232.113183] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> [ 1232.113319] kworker/3:0 D11984 4609 2 0x00000800 >> [ 1232.113416] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func >> [ 1232.113531] Call Trace: >> [ 1232.113579] [c0000000fb2db7a0] [c0000000fb2db900] 0xc0000000fb2db900 (unreliable) >> [ 1232.113717] [c0000000fb2db970] [c00000000001c964] __switch_to+0x304/0x6e0 >> [ 1232.113840] [c0000000fb2dba10] [c000000000a408c0] __schedule+0x2e0/0xa80 >> [ 1232.113978] [c0000000fb2dbae0] [c000000000a410a8] schedule+0x48/0xc0 >> [ 1232.114113] [c0000000fb2dbb10] [c000000000a44d88] rwsem_down_read_failed+0x128/0x1b0 >> [ 1232.114269] [c0000000fb2dbb70] [c0000000001696a8] __percpu_down_read+0x108/0x110 >> [ 1232.114426] [c0000000fb2dbba0] [c00000000032e498] get_online_mems+0x68/0x80 >> [ 1232.115487] [c0000000fb2dbbc0] [c0000000002c82ec] memcg_create_kmem_cache+0x4c/0x190 >> [ 1232.115651] [c0000000fb2dbc60] [c0000000003483b8] memcg_kmem_cache_create_func+0x38/0xf0 >> [ 1232.115809] [c0000000fb2dbc90] [c000000000121594] process_one_work+0x2b4/0x590 >> [ 1232.115964] [c0000000fb2dbd20] [c000000000121908] worker_thread+0x98/0x5d0 >> [ 1232.116095] [c0000000fb2dbdc0] [c00000000012a134] kthread+0x164/0x1b0 >> [ 1232.116229] [c0000000fb2dbe30] [c00000000000bae0] ret_from_kernel_thread+0x5c/0x7c > > I do not see how this is related to the offline path. It's blocked doing get_online_mems(). So it's unrelated to the offline, but it can't proceed until the offline finishes, which it never does, IIUIC. cheers -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
Michael Ellerman <mpe@ellerman.id.au> writes: > Michal Hocko <mhocko@kernel.org> writes: >> On Tue 10-10-17 23:05:08, Michael Ellerman wrote: >>> Michal Hocko <mhocko@kernel.org> writes: >>> > From: Michal Hocko <mhocko@suse.com> >>> > Memory offlining can fail just too eagerly under a heavy memory pressure. >>> > >>> > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 >>> > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) >>> > [ 5410.336811] page dumped because: isolation failed >>> > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 >>> > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed >>> > >>> > Isolation has failed here because the page is not on LRU. Most probably >>> > because it was on the pcp LRU cache or it has been removed from the LRU >>> > already but it hasn't been freed yet. In both cases the page doesn't look >>> > non-migrable so retrying more makes sense. >>> >>> This breaks offline for me. >>> >>> Prior to this commit: >>> /sys/devices/system/memory/memory0# time echo 0 > online >>> -bash: echo: write error: Device or resource busy >>> >>> real 0m0.001s >>> user 0m0.000s >>> sys 0m0.001s >>> >>> After: >>> /sys/devices/system/memory/memory0# time echo 0 > online >>> -bash: echo: write error: Device or resource busy >>> >>> real 2m0.009s >>> user 0m0.000s >>> sys 1m25.035s >>> >>> There's no way that block can be removed, it contains the kernel text, >>> so it should instantly fail - which it used to. >> >> OK, that means that start_isolate_page_range should have failed but it >> hasn't for some reason. I strongly suspect has_unmovable_pages is doing >> something wrong. Is the kernel text marked somehow? E.g. PageReserved? > > I'm not sure how the text is marked, will have to dig into that. Yeah it's reserved: $ grep __init_begin /proc/kallsyms c000000000d70000 T __init_begin $ ./page-types -r -a 0x0,0xd7 flags page-count MB symbolic-flags long-symbolic-flags 0x0000000100000000 215 13 __________________________r_______________ reserved total 215 13 I added some printks, we're getting EBUSY from do_migrate_range(pfn, end_pfn). So we seem to just have an infinite loop: repeat: /* start memory hot removal */ ret = -EINTR; if (signal_pending(current)) goto failed_removal; cond_resched(); lru_add_drain_all_cpuslocked(); drain_all_pages(zone); pfn = scan_movable_pages(start_pfn, end_pfn); if (pfn) { /* We have movable pages */ ret = do_migrate_range(pfn, end_pfn); printk_ratelimited("memory-hotplug: migrate range returned %ld\n", ret); goto repeat; } eg: memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 __offline_pages: 354031 callbacks suppressed memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 memory-hotplug: migrate range returned -16 __offline_pages: 355794 callbacks suppressed cheers -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Wed 11-10-17 13:37:50, Michael Ellerman wrote: > Michal Hocko <mhocko@kernel.org> writes: > > > On Tue 10-10-17 23:05:08, Michael Ellerman wrote: > >> Michal Hocko <mhocko@kernel.org> writes: > >> > >> > From: Michal Hocko <mhocko@suse.com> > >> > > >> > Memory offlining can fail just too eagerly under a heavy memory pressure. > >> > > >> > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 > >> > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) > >> > [ 5410.336811] page dumped because: isolation failed > >> > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 > >> > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed > >> > > >> > Isolation has failed here because the page is not on LRU. Most probably > >> > because it was on the pcp LRU cache or it has been removed from the LRU > >> > already but it hasn't been freed yet. In both cases the page doesn't look > >> > non-migrable so retrying more makes sense. > >> > >> This breaks offline for me. > >> > >> Prior to this commit: > >> /sys/devices/system/memory/memory0# time echo 0 > online > >> -bash: echo: write error: Device or resource busy > >> > >> real 0m0.001s > >> user 0m0.000s > >> sys 0m0.001s > >> > >> After: > >> /sys/devices/system/memory/memory0# time echo 0 > online > >> -bash: echo: write error: Device or resource busy > >> > >> real 2m0.009s > >> user 0m0.000s > >> sys 1m25.035s > >> > >> > >> There's no way that block can be removed, it contains the kernel text, > >> so it should instantly fail - which it used to. > > > > OK, that means that start_isolate_page_range should have failed but it > > hasn't for some reason. I strongly suspect has_unmovable_pages is doing > > something wrong. Is the kernel text marked somehow? E.g. PageReserved? > > I'm not sure how the text is marked, will have to dig into that. > > > In other words, does the diff below helps? > > No that doesn't help. This is really strange! As you write in other email the page is reserved. That means that some of the earlier checks if (zone_idx(zone) == ZONE_MOVABLE) return false; mt = get_pageblock_migratetype(page); if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) return false; has bailed out early. I would be quite surprised if the kernel text was sitting in the zone movable. The migrate type check is more fishy AFAICS. I can imagine that the kernel text can share the movable or CMA mt block. I am not really familiar with this function but it looks suspicious. So does it help to remove this check? --- diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3badcedf96a7..5b4d85ae445c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7355,9 +7355,6 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, */ if (zone_idx(zone) == ZONE_MOVABLE) return false; - mt = get_pageblock_migratetype(page); - if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) - return false; pfn = page_to_pfn(page); for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { @@ -7368,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, page = pfn_to_page(check); + if (PageReserved(page)) + return true; + /* * Hugepages are not in LRU lists, but they're movable. * We need not scan over tail pages bacause we don't -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 10/11/2017 08:51 AM, Michal Hocko wrote: > On Wed 11-10-17 13:37:50, Michael Ellerman wrote: >> Michal Hocko <mhocko@kernel.org> writes: >> >>> On Tue 10-10-17 23:05:08, Michael Ellerman wrote: >>>> Michal Hocko <mhocko@kernel.org> writes: >>>> >>>>> From: Michal Hocko <mhocko@suse.com> >>>>> >>>>> Memory offlining can fail just too eagerly under a heavy memory pressure. >>>>> >>>>> [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 >>>>> [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) >>>>> [ 5410.336811] page dumped because: isolation failed >>>>> [ 5410.336813] page->mem_cgroup:ffff8801cd662000 >>>>> [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed >>>>> >>>>> Isolation has failed here because the page is not on LRU. Most probably >>>>> because it was on the pcp LRU cache or it has been removed from the LRU >>>>> already but it hasn't been freed yet. In both cases the page doesn't look >>>>> non-migrable so retrying more makes sense. >>>> >>>> This breaks offline for me. >>>> >>>> Prior to this commit: >>>> /sys/devices/system/memory/memory0# time echo 0 > online >>>> -bash: echo: write error: Device or resource busy Well, that means offline didn't actually work for that block even before this patch, right? Is it even a movable_node block? I guess not? >>>> real 0m0.001s >>>> user 0m0.000s >>>> sys 0m0.001s >>>> >>>> After: >>>> /sys/devices/system/memory/memory0# time echo 0 > online >>>> -bash: echo: write error: Device or resource busy >>>> >>>> real 2m0.009s >>>> user 0m0.000s >>>> sys 1m25.035s >>>> >>>> >>>> There's no way that block can be removed, it contains the kernel text, >>>> so it should instantly fail - which it used to. Ah, right. So your complain is really about that the failure is not instant anymore for blocks that can't be offlined. >>> OK, that means that start_isolate_page_range should have failed but it >>> hasn't for some reason. I strongly suspect has_unmovable_pages is doing >>> something wrong. Is the kernel text marked somehow? E.g. PageReserved? >> >> I'm not sure how the text is marked, will have to dig into that. >> >>> In other words, does the diff below helps? >> >> No that doesn't help. > > This is really strange! As you write in other email the page is > reserved. That means that some of the earlier checks > if (zone_idx(zone) == ZONE_MOVABLE) > return false; > mt = get_pageblock_migratetype(page); > if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) The MIGRATE_MOVABLE check is indeed bogus, because that doesn't guarantee there are no unmovable pages in the block (CMA block OTOH should be a guarantee). > return false; > has bailed out early. I would be quite surprised if the kernel text was > sitting in the zone movable. The migrate type check is more fishy > AFAICS. I can imagine that the kernel text can share the movable or CMA > mt block. I am not really familiar with this function but it looks > suspicious. So does it help to remove this check? > --- > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3badcedf96a7..5b4d85ae445c 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7355,9 +7355,6 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > */ > if (zone_idx(zone) == ZONE_MOVABLE) > return false; > - mt = get_pageblock_migratetype(page); > - if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) > - return false; > > pfn = page_to_pfn(page); > for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { > @@ -7368,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > > page = pfn_to_page(check); > > + if (PageReserved(page)) > + return true; > + > /* > * Hugepages are not in LRU lists, but they're movable. > * We need not scan over tail pages bacause we don't > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Wed 11-10-17 10:04:39, Vlastimil Babka wrote: > On 10/11/2017 08:51 AM, Michal Hocko wrote: [...] > > This is really strange! As you write in other email the page is > > reserved. That means that some of the earlier checks > > if (zone_idx(zone) == ZONE_MOVABLE) > > return false; > > mt = get_pageblock_migratetype(page); > > if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) > > The MIGRATE_MOVABLE check is indeed bogus, because that doesn't > guarantee there are no unmovable pages in the block (CMA block OTOH > should be a guarantee). OK, thanks for confirmation. I will remove the MIGRATE_MOVABLE check here. Do you think it is worth removing CMA check as well? This is merely an optimization AFAIU because we do not have to check the full pageblockworth of pfns. Anyway, let's way for Michael to confirm it really helps. If yes I will post a full patch and ask Andrew to add it as a prerequisite for this patch when sending to Linus to prevent the regression. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 10/11/2017 10:13 AM, Michal Hocko wrote: > On Wed 11-10-17 10:04:39, Vlastimil Babka wrote: >> On 10/11/2017 08:51 AM, Michal Hocko wrote: > [...] >>> This is really strange! As you write in other email the page is >>> reserved. That means that some of the earlier checks >>> if (zone_idx(zone) == ZONE_MOVABLE) >>> return false; >>> mt = get_pageblock_migratetype(page); >>> if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) >> >> The MIGRATE_MOVABLE check is indeed bogus, because that doesn't >> guarantee there are no unmovable pages in the block (CMA block OTOH >> should be a guarantee). > > OK, thanks for confirmation. I will remove the MIGRATE_MOVABLE check > here. Do you think it is worth removing CMA check as well? This is > merely an optimization AFAIU because we do not have to check the full > pageblockworth of pfns. Actually, we should remove the CMA part as well. It's true that MIGRATE_CMA does guarantee that the *buddy allocator* won't allocate non-MOVABLE pages from the pageblock. But if the memory got allocated as an actual CMA allocation (alloc_contig...) it will almost certainly not be movable. > Anyway, let's way for Michael to confirm it really helps. If yes I will > post a full patch and ask Andrew to add it as a prerequisite for this > patch when sending to Linus to prevent the regression. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Wed 11-10-17 13:17:13, Vlastimil Babka wrote: > On 10/11/2017 10:13 AM, Michal Hocko wrote: > > On Wed 11-10-17 10:04:39, Vlastimil Babka wrote: > >> On 10/11/2017 08:51 AM, Michal Hocko wrote: > > [...] > >>> This is really strange! As you write in other email the page is > >>> reserved. That means that some of the earlier checks > >>> if (zone_idx(zone) == ZONE_MOVABLE) > >>> return false; > >>> mt = get_pageblock_migratetype(page); > >>> if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) > >> > >> The MIGRATE_MOVABLE check is indeed bogus, because that doesn't > >> guarantee there are no unmovable pages in the block (CMA block OTOH > >> should be a guarantee). > > > > OK, thanks for confirmation. I will remove the MIGRATE_MOVABLE check > > here. Do you think it is worth removing CMA check as well? This is > > merely an optimization AFAIU because we do not have to check the full > > pageblockworth of pfns. > > Actually, we should remove the CMA part as well. It's true that > MIGRATE_CMA does guarantee that the *buddy allocator* won't allocate > non-MOVABLE pages from the pageblock. But if the memory got allocated as > an actual CMA allocation (alloc_contig...) it will almost certainly not > be movable. That was my suspicious. Thanks! -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 10/11/2017 10:49 AM, Michael Ellerman wrote: > Michael Ellerman <mpe@ellerman.id.au> writes: >> Michal Hocko <mhocko@kernel.org> writes: >>> On Tue 10-10-17 23:05:08, Michael Ellerman wrote: >>>> Michal Hocko <mhocko@kernel.org> writes: >>>>> From: Michal Hocko <mhocko@suse.com> >>>>> Memory offlining can fail just too eagerly under a heavy memory pressure. >>>>> >>>>> [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 >>>>> [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) >>>>> [ 5410.336811] page dumped because: isolation failed >>>>> [ 5410.336813] page->mem_cgroup:ffff8801cd662000 >>>>> [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed >>>>> >>>>> Isolation has failed here because the page is not on LRU. Most probably >>>>> because it was on the pcp LRU cache or it has been removed from the LRU >>>>> already but it hasn't been freed yet. In both cases the page doesn't look >>>>> non-migrable so retrying more makes sense. >>>> This breaks offline for me. >>>> >>>> Prior to this commit: >>>> /sys/devices/system/memory/memory0# time echo 0 > online >>>> -bash: echo: write error: Device or resource busy >>>> >>>> real 0m0.001s >>>> user 0m0.000s >>>> sys 0m0.001s >>>> >>>> After: >>>> /sys/devices/system/memory/memory0# time echo 0 > online >>>> -bash: echo: write error: Device or resource busy >>>> >>>> real 2m0.009s >>>> user 0m0.000s >>>> sys 1m25.035s >>>> >>>> There's no way that block can be removed, it contains the kernel text, >>>> so it should instantly fail - which it used to. >>> OK, that means that start_isolate_page_range should have failed but it >>> hasn't for some reason. I strongly suspect has_unmovable_pages is doing >>> something wrong. Is the kernel text marked somehow? E.g. PageReserved? >> I'm not sure how the text is marked, will have to dig into that. > Yeah it's reserved: > > $ grep __init_begin /proc/kallsyms > c000000000d70000 T __init_begin > $ ./page-types -r -a 0x0,0xd7 > flags page-count MB symbolic-flags long-symbolic-flags > 0x0000000100000000 215 13 __________________________r_______________ reserved > total 215 13 Hey Michael, What tool is this 'page-types' ? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Wed 11-10-17 19:35:04, Anshuman Khandual wrote: [...] > > $ grep __init_begin /proc/kallsyms > > c000000000d70000 T __init_begin > > $ ./page-types -r -a 0x0,0xd7 > > flags page-count MB symbolic-flags long-symbolic-flags > > 0x0000000100000000 215 13 __________________________r_______________ reserved > > total 215 13 > > Hey Michael, > > What tool is this 'page-types' ? tools/vm/page-types.c -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
Vlastimil Babka <vbabka@suse.cz> writes: > On 10/11/2017 08:51 AM, Michal Hocko wrote: >> On Wed 11-10-17 13:37:50, Michael Ellerman wrote: >>> Michal Hocko <mhocko@kernel.org> writes: >>>> On Tue 10-10-17 23:05:08, Michael Ellerman wrote: >>>>> Michal Hocko <mhocko@kernel.org> writes: >>>>>> From: Michal Hocko <mhocko@suse.com> >>>>>> >>>>>> Memory offlining can fail just too eagerly under a heavy memory pressure. ... >>>>> >>>>> This breaks offline for me. >>>>> >>>>> Prior to this commit: >>>>> /sys/devices/system/memory/memory0# time echo 0 > online >>>>> -bash: echo: write error: Device or resource busy > > Well, that means offline didn't actually work for that block even before > this patch, right? Is it even a movable_node block? I guess not? Correct. It should fail. >>>>> After: >>>>> /sys/devices/system/memory/memory0# time echo 0 > online >>>>> -bash: echo: write error: Device or resource busy >>>>> >>>>> real 2m0.009s >>>>> user 0m0.000s >>>>> sys 1m25.035s >>>>> >>>>> There's no way that block can be removed, it contains the kernel text, >>>>> so it should instantly fail - which it used to. > > Ah, right. So your complain is really about that the failure is not > instant anymore for blocks that can't be offlined. Yes. Previously it failed instantly, now it doesn't fail, and loops infinitely (once the 2 minute limit is removed). >> This is really strange! As you write in other email the page is >> reserved. That means that some of the earlier checks >> if (zone_idx(zone) == ZONE_MOVABLE) >> return false; >> mt = get_pageblock_migratetype(page); >> if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) > > The MIGRATE_MOVABLE check is indeed bogus, because that doesn't > guarantee there are no unmovable pages in the block (CMA block OTOH > should be a guarantee). OK I'll try that and get back to you. cheers >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 3badcedf96a7..5b4d85ae445c 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -7355,9 +7355,6 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, >> */ >> if (zone_idx(zone) == ZONE_MOVABLE) >> return false; >> - mt = get_pageblock_migratetype(page); >> - if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) >> - return false; >> >> pfn = page_to_pfn(page); >> for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { >> @@ -7368,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, >> >> page = pfn_to_page(check); >> >> + if (PageReserved(page)) >> + return true; >> + >> /* >> * Hugepages are not in LRU lists, but they're movable. >> * We need not scan over tail pages bacause we don't >> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Fri 13-10-17 22:42:46, Michael Ellerman wrote: > Vlastimil Babka <vbabka@suse.cz> writes: > > On 10/11/2017 08:51 AM, Michal Hocko wrote: > >> On Wed 11-10-17 13:37:50, Michael Ellerman wrote: > >>> Michal Hocko <mhocko@kernel.org> writes: > >>>> On Tue 10-10-17 23:05:08, Michael Ellerman wrote: > >>>>> Michal Hocko <mhocko@kernel.org> writes: > >>>>>> From: Michal Hocko <mhocko@suse.com> > >>>>>> > >>>>>> Memory offlining can fail just too eagerly under a heavy memory pressure. > ... > >>>>> > >>>>> This breaks offline for me. > >>>>> > >>>>> Prior to this commit: > >>>>> /sys/devices/system/memory/memory0# time echo 0 > online > >>>>> -bash: echo: write error: Device or resource busy > > > > Well, that means offline didn't actually work for that block even before > > this patch, right? Is it even a movable_node block? I guess not? > > Correct. It should fail. > > >>>>> After: > >>>>> /sys/devices/system/memory/memory0# time echo 0 > online > >>>>> -bash: echo: write error: Device or resource busy > >>>>> > >>>>> real 2m0.009s > >>>>> user 0m0.000s > >>>>> sys 1m25.035s > >>>>> > >>>>> There's no way that block can be removed, it contains the kernel text, > >>>>> so it should instantly fail - which it used to. > > > > Ah, right. So your complain is really about that the failure is not > > instant anymore for blocks that can't be offlined. > > Yes. Previously it failed instantly, now it doesn't fail, and loops > infinitely (once the 2 minute limit is removed). Yeah it failed only because the migration code retried few times and we bailed out which is wrong as well. I will send two patches as a reply to this email. > >> This is really strange! As you write in other email the page is > >> reserved. That means that some of the earlier checks > >> if (zone_idx(zone) == ZONE_MOVABLE) > >> return false; > >> mt = get_pageblock_migratetype(page); > >> if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) > > > > The MIGRATE_MOVABLE check is indeed bogus, because that doesn't > > guarantee there are no unmovable pages in the block (CMA block OTOH > > should be a guarantee). > > OK I'll try that and get back to you. Thanks! -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
From: Michal Hocko <mhocko@suse.com> Michael has noticed that the memory offline tries to migrate kernel code pages when doing echo 0 > /sys/devices/system/memory/memory0/online The current implementation will fail the operation after several failed page migration attempts but we shouldn't even attempt to migrate that memory and fail right away because this memory is clearly not migrateable. This will become a real problem when we drop the retry loop counter resp. timeout. The real problem is in has_unmovable_pages in fact. We should fail if there are any non migrateable pages in the area. In orther to guarantee that remove the migrate type checks because MIGRATE_MOVABLE is not guaranteed to contain only migrateable pages. It is merely a heuristic. Similarly MIGRATE_CMA does guarantee that the page allocator doesn't allocate any non-migrateable pages from the block but CMA allocations themselves are unlikely to migrateable. Therefore remove both checks. Reported-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Michal Hocko <mhocko@suse.com> --- mm/page_alloc.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3badcedf96a7..ad0294ab3e4f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7355,9 +7355,6 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, */ if (zone_idx(zone) == ZONE_MOVABLE) return false; - mt = get_pageblock_migratetype(page); - if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) - return false; pfn = page_to_pfn(page); for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { -- 2.14.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
From: Michal Hocko <mhocko@suse.com> Reserved pages should be completely ignored by the core mm because they have a special meaning for their owners. has_unmovable_pages doesn't check those so we rely on other tests (reference count, or PageLRU) to fail on such pages. Althought this happens to work it is safer to simply check for those explicitly and do not rely on the owner of the page to abuse those fields for special purposes. Please note that this is more of a further fortification of the code rahter than a fix of an existing issue. Signed-off-by: Michal Hocko <mhocko@suse.com> --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ad0294ab3e4f..a8800b0a5619 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7365,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, page = pfn_to_page(check); + if (PageReferenced(page)) + return true; + /* * Hugepages are not in LRU lists, but they're movable. * We need not scan over tail pages bacause we don't -- 2.14.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 10/13/2017 02:00 PM, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > Reserved pages should be completely ignored by the core mm because they > have a special meaning for their owners. has_unmovable_pages doesn't > check those so we rely on other tests (reference count, or PageLRU) to > fail on such pages. Althought this happens to work it is safer to simply > check for those explicitly and do not rely on the owner of the page > to abuse those fields for special purposes. > > Please note that this is more of a further fortification of the code > rahter than a fix of an existing issue. > > Signed-off-by: Michal Hocko <mhocko@suse.com> > --- > mm/page_alloc.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ad0294ab3e4f..a8800b0a5619 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7365,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > > page = pfn_to_page(check); > > + if (PageReferenced(page)) "Referenced" != "Reserved" > + return true; > + > /* > * Hugepages are not in LRU lists, but they're movable. > * We need not scan over tail pages bacause we don't > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Fri 13-10-17 14:04:08, Vlastimil Babka wrote:
> On 10/13/2017 02:00 PM, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@suse.com>
> >
> > Reserved pages should be completely ignored by the core mm because they
> > have a special meaning for their owners. has_unmovable_pages doesn't
> > check those so we rely on other tests (reference count, or PageLRU) to
> > fail on such pages. Althought this happens to work it is safer to simply
> > check for those explicitly and do not rely on the owner of the page
> > to abuse those fields for special purposes.
> >
> > Please note that this is more of a further fortification of the code
> > rahter than a fix of an existing issue.
> >
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
> > ---
> > mm/page_alloc.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index ad0294ab3e4f..a8800b0a5619 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -7365,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
> >
> > page = pfn_to_page(check);
> >
> > + if (PageReferenced(page))
>
> "Referenced" != "Reserved"
Dohh, you are right of course. I blame auto-completion ;) but I am lame
in fact...
---
Michal Hocko <mhocko@kernel.org> writes: > From: Michal Hocko <mhocko@suse.com> > > Michael has noticed that the memory offline tries to migrate kernel code > pages when doing > echo 0 > /sys/devices/system/memory/memory0/online > > The current implementation will fail the operation after several failed > page migration attempts but we shouldn't even attempt to migrate > that memory and fail right away because this memory is clearly not > migrateable. This will become a real problem when we drop the retry loop > counter resp. timeout. > > The real problem is in has_unmovable_pages in fact. We should fail if > there are any non migrateable pages in the area. In orther to guarantee > that remove the migrate type checks because MIGRATE_MOVABLE is not > guaranteed to contain only migrateable pages. It is merely a heuristic. > Similarly MIGRATE_CMA does guarantee that the page allocator doesn't > allocate any non-migrateable pages from the block but CMA allocations > themselves are unlikely to migrateable. Therefore remove both checks. > > Reported-by: Michael Ellerman <mpe@ellerman.id.au> > Signed-off-by: Michal Hocko <mhocko@suse.com> Thanks, that works for me. Tested-by: Michael Ellerman <mpe@ellerman.id.au> cheers -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Tue 17-10-17 22:41:08, Michael Ellerman wrote: > Michal Hocko <mhocko@kernel.org> writes: > > > From: Michal Hocko <mhocko@suse.com> > > > > Michael has noticed that the memory offline tries to migrate kernel code > > pages when doing > > echo 0 > /sys/devices/system/memory/memory0/online > > > > The current implementation will fail the operation after several failed > > page migration attempts but we shouldn't even attempt to migrate > > that memory and fail right away because this memory is clearly not > > migrateable. This will become a real problem when we drop the retry loop > > counter resp. timeout. > > > > The real problem is in has_unmovable_pages in fact. We should fail if > > there are any non migrateable pages in the area. In orther to guarantee > > that remove the migrate type checks because MIGRATE_MOVABLE is not > > guaranteed to contain only migrateable pages. It is merely a heuristic. > > Similarly MIGRATE_CMA does guarantee that the page allocator doesn't > > allocate any non-migrateable pages from the block but CMA allocations > > themselves are unlikely to migrateable. Therefore remove both checks. > > > > Reported-by: Michael Ellerman <mpe@ellerman.id.au> > > Signed-off-by: Michal Hocko <mhocko@suse.com> > > Thanks, that works for me. > > Tested-by: Michael Ellerman <mpe@ellerman.id.au> Thanks a lot Michael! Andrew, could you add these two patches and merge them before mm-memory_hotplug-do-not-fail-offlining-too-early.patch? Or should I rather repost the full series (including 2 already merged patches? again? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 10/13/2017 02:00 PM, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > Michael has noticed that the memory offline tries to migrate kernel code > pages when doing > echo 0 > /sys/devices/system/memory/memory0/online > > The current implementation will fail the operation after several failed > page migration attempts but we shouldn't even attempt to migrate > that memory and fail right away because this memory is clearly not > migrateable. This will become a real problem when we drop the retry loop > counter resp. timeout. > > The real problem is in has_unmovable_pages in fact. We should fail if > there are any non migrateable pages in the area. In orther to guarantee > that remove the migrate type checks because MIGRATE_MOVABLE is not > guaranteed to contain only migrateable pages. It is merely a heuristic. > Similarly MIGRATE_CMA does guarantee that the page allocator doesn't > allocate any non-migrateable pages from the block but CMA allocations > themselves are unlikely to migrateable. Therefore remove both checks. > > Reported-by: Michael Ellerman <mpe@ellerman.id.au> > Signed-off-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > mm/page_alloc.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3badcedf96a7..ad0294ab3e4f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7355,9 +7355,6 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > */ > if (zone_idx(zone) == ZONE_MOVABLE) > return false; > - mt = get_pageblock_migratetype(page); > - if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) > - return false; > > pfn = page_to_pfn(page); > for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 10/13/2017 02:07 PM, Michal Hocko wrote: > On Fri 13-10-17 14:04:08, Vlastimil Babka wrote: >> On 10/13/2017 02:00 PM, Michal Hocko wrote: >>> From: Michal Hocko <mhocko@suse.com> >>> >>> Reserved pages should be completely ignored by the core mm because they >>> have a special meaning for their owners. has_unmovable_pages doesn't >>> check those so we rely on other tests (reference count, or PageLRU) to >>> fail on such pages. Althought this happens to work it is safer to simply >>> check for those explicitly and do not rely on the owner of the page >>> to abuse those fields for special purposes. >>> >>> Please note that this is more of a further fortification of the code >>> rahter than a fix of an existing issue. >>> >>> Signed-off-by: Michal Hocko <mhocko@suse.com> >>> --- >>> mm/page_alloc.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index ad0294ab3e4f..a8800b0a5619 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -7365,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, >>> >>> page = pfn_to_page(check); >>> >>> + if (PageReferenced(page)) >> >> "Referenced" != "Reserved" > > Dohh, you are right of course. I blame auto-completion ;) but I am lame > in fact... > --- > From 44b20bdb03846bc5fd79c883d16b8f3aa436878f Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@suse.com> > Date: Fri, 13 Oct 2017 13:55:21 +0200 > Subject: [PATCH] mm, page_alloc: fail has_unmovable_pages when seeing reserved > pages > > Reserved pages should be completely ignored by the core mm because they > have a special meaning for their owners. has_unmovable_pages doesn't > check those so we rely on other tests (reference count, or PageLRU) to > fail on such pages. Althought this happens to work it is safer to simply > check for those explicitly and do not rely on the owner of the page > to abuse those fields for special purposes. > > Please note that this is more of a further fortification of the code > rahter than a fix of an existing issue. > > Signed-off-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > mm/page_alloc.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ad0294ab3e4f..5b4d85ae445c 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7365,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > > page = pfn_to_page(check); > > + if (PageReserved(page)) > + return true; > + > /* > * Hugepages are not in LRU lists, but they're movable. > * We need not scan over tail pages bacause we don't > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Fri, Oct 13, 2017 at 02:00:12PM +0200, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > Michael has noticed that the memory offline tries to migrate kernel code > pages when doing > echo 0 > /sys/devices/system/memory/memory0/online > > The current implementation will fail the operation after several failed > page migration attempts but we shouldn't even attempt to migrate > that memory and fail right away because this memory is clearly not > migrateable. This will become a real problem when we drop the retry loop > counter resp. timeout. > > The real problem is in has_unmovable_pages in fact. We should fail if > there are any non migrateable pages in the area. In orther to guarantee > that remove the migrate type checks because MIGRATE_MOVABLE is not > guaranteed to contain only migrateable pages. It is merely a heuristic. > Similarly MIGRATE_CMA does guarantee that the page allocator doesn't > allocate any non-migrateable pages from the block but CMA allocations > themselves are unlikely to migrateable. Therefore remove both checks. Hello, This patch will break the CMA user. As you mentioned, CMA allocation itself isn't migrateable. So, after a single page is allocated through CMA allocation, has_unmovable_pages() will return true for this pageblock. Then, futher CMA allocation request to this pageblock will fail because it requires isolating the pageblock. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > On Fri, Oct 13, 2017 at 02:00:12PM +0200, Michal Hocko wrote: > > From: Michal Hocko <mhocko@suse.com> > > > > Michael has noticed that the memory offline tries to migrate kernel code > > pages when doing > > echo 0 > /sys/devices/system/memory/memory0/online > > > > The current implementation will fail the operation after several failed > > page migration attempts but we shouldn't even attempt to migrate > > that memory and fail right away because this memory is clearly not > > migrateable. This will become a real problem when we drop the retry loop > > counter resp. timeout. > > > > The real problem is in has_unmovable_pages in fact. We should fail if > > there are any non migrateable pages in the area. In orther to guarantee > > that remove the migrate type checks because MIGRATE_MOVABLE is not > > guaranteed to contain only migrateable pages. It is merely a heuristic. > > Similarly MIGRATE_CMA does guarantee that the page allocator doesn't > > allocate any non-migrateable pages from the block but CMA allocations > > themselves are unlikely to migrateable. Therefore remove both checks. > > Hello, > > This patch will break the CMA user. As you mentioned, CMA allocation > itself isn't migrateable. So, after a single page is allocated through > CMA allocation, has_unmovable_pages() will return true for this > pageblock. Then, futher CMA allocation request to this pageblock will > fail because it requires isolating the pageblock. Hmm, does this mean that the CMA allocation path depends on has_unmovable_pages to return false here even though the memory is not movable? This sounds really strange to me and kind of abuse of this function. Which path is that? Can we do the migrate type test theres? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > > On Fri, Oct 13, 2017 at 02:00:12PM +0200, Michal Hocko wrote: > > > From: Michal Hocko <mhocko@suse.com> > > > > > > Michael has noticed that the memory offline tries to migrate kernel code > > > pages when doing > > > echo 0 > /sys/devices/system/memory/memory0/online > > > > > > The current implementation will fail the operation after several failed > > > page migration attempts but we shouldn't even attempt to migrate > > > that memory and fail right away because this memory is clearly not > > > migrateable. This will become a real problem when we drop the retry loop > > > counter resp. timeout. > > > > > > The real problem is in has_unmovable_pages in fact. We should fail if > > > there are any non migrateable pages in the area. In orther to guarantee > > > that remove the migrate type checks because MIGRATE_MOVABLE is not > > > guaranteed to contain only migrateable pages. It is merely a heuristic. > > > Similarly MIGRATE_CMA does guarantee that the page allocator doesn't > > > allocate any non-migrateable pages from the block but CMA allocations > > > themselves are unlikely to migrateable. Therefore remove both checks. > > > > Hello, > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > itself isn't migrateable. So, after a single page is allocated through > > CMA allocation, has_unmovable_pages() will return true for this > > pageblock. Then, futher CMA allocation request to this pageblock will > > fail because it requires isolating the pageblock. > > Hmm, does this mean that the CMA allocation path depends on > has_unmovable_pages to return false here even though the memory is not > movable? This sounds really strange to me and kind of abuse of this Your understanding is correct. Perhaps, abuse or wrong function name. > function. Which path is that? Can we do the migrate type test theres? alloc_contig_range() -> start_isolate_page_range() -> set_migratetype_isolate() -> has_unmovable_pages() We can add one argument, 'XXX' to set_migratetype_isolate() and change it to check migrate type rather than has_unmovable_pages() if 'XXX' is specified. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: [...] > > > Hello, > > > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > > itself isn't migrateable. So, after a single page is allocated through > > > CMA allocation, has_unmovable_pages() will return true for this > > > pageblock. Then, futher CMA allocation request to this pageblock will > > > fail because it requires isolating the pageblock. > > > > Hmm, does this mean that the CMA allocation path depends on > > has_unmovable_pages to return false here even though the memory is not > > movable? This sounds really strange to me and kind of abuse of this > > Your understanding is correct. Perhaps, abuse or wrong function name. > > > function. Which path is that? Can we do the migrate type test theres? > > alloc_contig_range() -> start_isolate_page_range() -> > set_migratetype_isolate() -> has_unmovable_pages() I see. It seems that the CMA and memory hotplug have a very different view on what should happen during isolation. > We can add one argument, 'XXX' to set_migratetype_isolate() and change > it to check migrate type rather than has_unmovable_pages() if 'XXX' is > specified. Can we use the migratetype argument and do the special thing for MIGRATE_CMA? Like the following diff? --- diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h index d4cd2014fa6f..fa9db0c7b54e 100644 --- a/include/linux/page-isolation.h +++ b/include/linux/page-isolation.h @@ -30,7 +30,7 @@ static inline bool is_migrate_isolate(int migratetype) #endif bool has_unmovable_pages(struct zone *zone, struct page *page, int count, - bool skip_hwpoisoned_pages); + int migratetype, bool skip_hwpoisoned_pages); void set_pageblock_migratetype(struct page *page, int migratetype); int move_freepages_block(struct zone *zone, struct page *page, int migratetype, int *num_movable); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index bc50d746a82f..ad2ea7069d14 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7362,6 +7362,7 @@ void *__init alloc_large_system_hash(const char *tablename, * race condition. So you can't expect this function should be exact. */ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, + int migratetype, bool skip_hwpoisoned_pages) { unsigned long pfn, iter, found; @@ -7373,6 +7374,15 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, if (zone_idx(zone) == ZONE_MOVABLE) return false; + /* + * CMA allocations (alloc_contig_range) really need to mark isolate + * CMA pageblocks even when they are not movable in fact so consider + * them movable here. + */ + if (is_migrate_cma(migratetype) && + is_migrate_cma(get_pageblock_migratetype(page))) + return false; + pfn = page_to_pfn(page); for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { unsigned long check = pfn + iter; @@ -7458,7 +7468,7 @@ bool is_pageblock_removable_nolock(struct page *page) if (!zone_spans_pfn(zone, pfn)) return false; - return !has_unmovable_pages(zone, page, 0, true); + return !has_unmovable_pages(zone, page, 0, MIGRATE_MOVABLE, true); } #if (defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || defined(CONFIG_CMA) diff --git a/mm/page_isolation.c b/mm/page_isolation.c index 757410d9f758..8616f5332c77 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -14,7 +14,7 @@ #define CREATE_TRACE_POINTS #include <trace/events/page_isolation.h> -static int set_migratetype_isolate(struct page *page, +static int set_migratetype_isolate(struct page *page, int migratetype, bool skip_hwpoisoned_pages) { struct zone *zone; @@ -51,7 +51,7 @@ static int set_migratetype_isolate(struct page *page, * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself. * We just check MOVABLE pages. */ - if (!has_unmovable_pages(zone, page, arg.pages_found, + if (!has_unmovable_pages(zone, page, arg.pages_found, migratetype, skip_hwpoisoned_pages)) ret = 0; @@ -63,14 +63,14 @@ static int set_migratetype_isolate(struct page *page, out: if (!ret) { unsigned long nr_pages; - int migratetype = get_pageblock_migratetype(page); + int mt = get_pageblock_migratetype(page); set_pageblock_migratetype(page, MIGRATE_ISOLATE); zone->nr_isolate_pageblock++; nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE, NULL); - __mod_zone_freepage_state(zone, -nr_pages, migratetype); + __mod_zone_freepage_state(zone, -nr_pages, mt); } spin_unlock_irqrestore(&zone->lock, flags); @@ -182,7 +182,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, pfn += pageblock_nr_pages) { page = __first_valid_page(pfn, pageblock_nr_pages); if (page && - set_migratetype_isolate(page, skip_hwpoisoned_pages)) { + set_migratetype_isolate(page, migratetype, skip_hwpoisoned_pages)) { undo_pfn = pfn; goto undo; } -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Thu 19-10-17 10:20:41, Michal Hocko wrote:
> On Thu 19-10-17 16:33:56, Joonsoo Kim wrote:
> > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote:
> > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote:
> [...]
> > > > Hello,
> > > >
> > > > This patch will break the CMA user. As you mentioned, CMA allocation
> > > > itself isn't migrateable. So, after a single page is allocated through
> > > > CMA allocation, has_unmovable_pages() will return true for this
> > > > pageblock. Then, futher CMA allocation request to this pageblock will
> > > > fail because it requires isolating the pageblock.
> > >
> > > Hmm, does this mean that the CMA allocation path depends on
> > > has_unmovable_pages to return false here even though the memory is not
> > > movable? This sounds really strange to me and kind of abuse of this
> >
> > Your understanding is correct. Perhaps, abuse or wrong function name.
> >
> > > function. Which path is that? Can we do the migrate type test theres?
> >
> > alloc_contig_range() -> start_isolate_page_range() ->
> > set_migratetype_isolate() -> has_unmovable_pages()
>
> I see. It seems that the CMA and memory hotplug have a very different
> view on what should happen during isolation.
>
> > We can add one argument, 'XXX' to set_migratetype_isolate() and change
> > it to check migrate type rather than has_unmovable_pages() if 'XXX' is
> > specified.
>
> Can we use the migratetype argument and do the special thing for
> MIGRATE_CMA? Like the following diff?
And with the full changelog.
---
On Thu, Oct 19, 2017 at 02:21:18PM +0200, Michal Hocko wrote: > On Thu 19-10-17 10:20:41, Michal Hocko wrote: > > On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: > > > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > > > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > > [...] > > > > > Hello, > > > > > > > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > > > > itself isn't migrateable. So, after a single page is allocated through > > > > > CMA allocation, has_unmovable_pages() will return true for this > > > > > pageblock. Then, futher CMA allocation request to this pageblock will > > > > > fail because it requires isolating the pageblock. > > > > > > > > Hmm, does this mean that the CMA allocation path depends on > > > > has_unmovable_pages to return false here even though the memory is not > > > > movable? This sounds really strange to me and kind of abuse of this > > > > > > Your understanding is correct. Perhaps, abuse or wrong function name. > > > > > > > function. Which path is that? Can we do the migrate type test theres? > > > > > > alloc_contig_range() -> start_isolate_page_range() -> > > > set_migratetype_isolate() -> has_unmovable_pages() > > > > I see. It seems that the CMA and memory hotplug have a very different > > view on what should happen during isolation. > > > > > We can add one argument, 'XXX' to set_migratetype_isolate() and change > > > it to check migrate type rather than has_unmovable_pages() if 'XXX' is > > > specified. > > > > Can we use the migratetype argument and do the special thing for > > MIGRATE_CMA? Like the following diff? > > And with the full changelog. > --- > >From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@suse.com> > Date: Thu, 19 Oct 2017 14:14:02 +0200 > Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > has_unmovable_pages > > Joonsoo has noticed that "mm: drop migrate type checks from > has_unmovable_pages" would break CMA allocator because it relies on > has_unmovable_pages returning false even for CMA pageblocks which in > fact don't have to be movable: > alloc_contig_range > start_isolate_page_range > set_migratetype_isolate > has_unmovable_pages > > This is a result of the code sharing between CMA and memory hotplug > while each one has a different idea of what has_unmovable_pages should > return. This is unfortunate but fixing it properly would require a lot > of code duplication. > > Fix the issue by introducing the requested migrate type argument > and special case MIGRATE_CMA case where CMA page blocks are handled > properly. This will work for memory hotplug because it requires > MIGRATE_MOVABLE. Unfortunately, alloc_contig_range() can be called with MIGRATE_MOVABLE so this patch cannot perfectly fix the problem. I did a more thinking and found that it's strange to check if there is unmovable page in the pageblock during the set_migratetype_isolate(). set_migratetype_isolate() should be just for setting the migratetype of the pageblock. Checking other things should be done by another place, for example, before calling the start_isolate_page_range() in __offline_pages(). Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Fri 20-10-17 11:13:29, Joonsoo Kim wrote: > On Thu, Oct 19, 2017 at 02:21:18PM +0200, Michal Hocko wrote: > > On Thu 19-10-17 10:20:41, Michal Hocko wrote: > > > On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: > > > > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > > > > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > > > [...] > > > > > > Hello, > > > > > > > > > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > > > > > itself isn't migrateable. So, after a single page is allocated through > > > > > > CMA allocation, has_unmovable_pages() will return true for this > > > > > > pageblock. Then, futher CMA allocation request to this pageblock will > > > > > > fail because it requires isolating the pageblock. > > > > > > > > > > Hmm, does this mean that the CMA allocation path depends on > > > > > has_unmovable_pages to return false here even though the memory is not > > > > > movable? This sounds really strange to me and kind of abuse of this > > > > > > > > Your understanding is correct. Perhaps, abuse or wrong function name. > > > > > > > > > function. Which path is that? Can we do the migrate type test theres? > > > > > > > > alloc_contig_range() -> start_isolate_page_range() -> > > > > set_migratetype_isolate() -> has_unmovable_pages() > > > > > > I see. It seems that the CMA and memory hotplug have a very different > > > view on what should happen during isolation. > > > > > > > We can add one argument, 'XXX' to set_migratetype_isolate() and change > > > > it to check migrate type rather than has_unmovable_pages() if 'XXX' is > > > > specified. > > > > > > Can we use the migratetype argument and do the special thing for > > > MIGRATE_CMA? Like the following diff? > > > > And with the full changelog. > > --- > > >From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > > From: Michal Hocko <mhocko@suse.com> > > Date: Thu, 19 Oct 2017 14:14:02 +0200 > > Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > > has_unmovable_pages > > > > Joonsoo has noticed that "mm: drop migrate type checks from > > has_unmovable_pages" would break CMA allocator because it relies on > > has_unmovable_pages returning false even for CMA pageblocks which in > > fact don't have to be movable: > > alloc_contig_range > > start_isolate_page_range > > set_migratetype_isolate > > has_unmovable_pages > > > > This is a result of the code sharing between CMA and memory hotplug > > while each one has a different idea of what has_unmovable_pages should > > return. This is unfortunate but fixing it properly would require a lot > > of code duplication. > > > > Fix the issue by introducing the requested migrate type argument > > and special case MIGRATE_CMA case where CMA page blocks are handled > > properly. This will work for memory hotplug because it requires > > MIGRATE_MOVABLE. > > Unfortunately, alloc_contig_range() can be called with > MIGRATE_MOVABLE so this patch cannot perfectly fix the problem. Yes, alloc_contig_range can be called with MIGRATE_MOVABLE but my understanding is that only CMA allocator really depends on this weird semantic and that does MIGRATE_CMA unconditionally. > I did a more thinking and found that it's strange to check if there is > unmovable page in the pageblock during the set_migratetype_isolate(). > set_migratetype_isolate() should be just for setting the migratetype > of the pageblock. Checking other things should be done by another > place, for example, before calling the start_isolate_page_range() in > __offline_pages(). How do we guarantee the atomicity? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Fri, Oct 20, 2017 at 07:59:22AM +0200, Michal Hocko wrote: > On Fri 20-10-17 11:13:29, Joonsoo Kim wrote: > > On Thu, Oct 19, 2017 at 02:21:18PM +0200, Michal Hocko wrote: > > > On Thu 19-10-17 10:20:41, Michal Hocko wrote: > > > > On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: > > > > > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > > > > > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > > > > [...] > > > > > > > Hello, > > > > > > > > > > > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > > > > > > itself isn't migrateable. So, after a single page is allocated through > > > > > > > CMA allocation, has_unmovable_pages() will return true for this > > > > > > > pageblock. Then, futher CMA allocation request to this pageblock will > > > > > > > fail because it requires isolating the pageblock. > > > > > > > > > > > > Hmm, does this mean that the CMA allocation path depends on > > > > > > has_unmovable_pages to return false here even though the memory is not > > > > > > movable? This sounds really strange to me and kind of abuse of this > > > > > > > > > > Your understanding is correct. Perhaps, abuse or wrong function name. > > > > > > > > > > > function. Which path is that? Can we do the migrate type test theres? > > > > > > > > > > alloc_contig_range() -> start_isolate_page_range() -> > > > > > set_migratetype_isolate() -> has_unmovable_pages() > > > > > > > > I see. It seems that the CMA and memory hotplug have a very different > > > > view on what should happen during isolation. > > > > > > > > > We can add one argument, 'XXX' to set_migratetype_isolate() and change > > > > > it to check migrate type rather than has_unmovable_pages() if 'XXX' is > > > > > specified. > > > > > > > > Can we use the migratetype argument and do the special thing for > > > > MIGRATE_CMA? Like the following diff? > > > > > > And with the full changelog. > > > --- > > > >From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > > > From: Michal Hocko <mhocko@suse.com> > > > Date: Thu, 19 Oct 2017 14:14:02 +0200 > > > Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > > > has_unmovable_pages > > > > > > Joonsoo has noticed that "mm: drop migrate type checks from > > > has_unmovable_pages" would break CMA allocator because it relies on > > > has_unmovable_pages returning false even for CMA pageblocks which in > > > fact don't have to be movable: > > > alloc_contig_range > > > start_isolate_page_range > > > set_migratetype_isolate > > > has_unmovable_pages > > > > > > This is a result of the code sharing between CMA and memory hotplug > > > while each one has a different idea of what has_unmovable_pages should > > > return. This is unfortunate but fixing it properly would require a lot > > > of code duplication. > > > > > > Fix the issue by introducing the requested migrate type argument > > > and special case MIGRATE_CMA case where CMA page blocks are handled > > > properly. This will work for memory hotplug because it requires > > > MIGRATE_MOVABLE. > > > > Unfortunately, alloc_contig_range() can be called with > > MIGRATE_MOVABLE so this patch cannot perfectly fix the problem. > > Yes, alloc_contig_range can be called with MIGRATE_MOVABLE but my > understanding is that only CMA allocator really depends on this weird > semantic and that does MIGRATE_CMA unconditionally. alloc_contig_range() could be called for partial pages in the pageblock. With your patch, this case also fails unnecessarilly if the other pages in the pageblock is pinned. Until now, there is no user calling alloc_contig_range() with partial pages except CMA allocator but API could support it. > > > I did a more thinking and found that it's strange to check if there is > > unmovable page in the pageblock during the set_migratetype_isolate(). > > set_migratetype_isolate() should be just for setting the migratetype > > of the pageblock. Checking other things should be done by another > > place, for example, before calling the start_isolate_page_range() in > > __offline_pages(). > > How do we guarantee the atomicity? What atomicity do you mean? Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Fri 20-10-17 15:50:14, Joonsoo Kim wrote: > On Fri, Oct 20, 2017 at 07:59:22AM +0200, Michal Hocko wrote: > > On Fri 20-10-17 11:13:29, Joonsoo Kim wrote: > > > On Thu, Oct 19, 2017 at 02:21:18PM +0200, Michal Hocko wrote: > > > > On Thu 19-10-17 10:20:41, Michal Hocko wrote: > > > > > On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: > > > > > > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > > > > > > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > > > > > [...] > > > > > > > > Hello, > > > > > > > > > > > > > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > > > > > > > itself isn't migrateable. So, after a single page is allocated through > > > > > > > > CMA allocation, has_unmovable_pages() will return true for this > > > > > > > > pageblock. Then, futher CMA allocation request to this pageblock will > > > > > > > > fail because it requires isolating the pageblock. > > > > > > > > > > > > > > Hmm, does this mean that the CMA allocation path depends on > > > > > > > has_unmovable_pages to return false here even though the memory is not > > > > > > > movable? This sounds really strange to me and kind of abuse of this > > > > > > > > > > > > Your understanding is correct. Perhaps, abuse or wrong function name. > > > > > > > > > > > > > function. Which path is that? Can we do the migrate type test theres? > > > > > > > > > > > > alloc_contig_range() -> start_isolate_page_range() -> > > > > > > set_migratetype_isolate() -> has_unmovable_pages() > > > > > > > > > > I see. It seems that the CMA and memory hotplug have a very different > > > > > view on what should happen during isolation. > > > > > > > > > > > We can add one argument, 'XXX' to set_migratetype_isolate() and change > > > > > > it to check migrate type rather than has_unmovable_pages() if 'XXX' is > > > > > > specified. > > > > > > > > > > Can we use the migratetype argument and do the special thing for > > > > > MIGRATE_CMA? Like the following diff? > > > > > > > > And with the full changelog. > > > > --- > > > > >From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > > > > From: Michal Hocko <mhocko@suse.com> > > > > Date: Thu, 19 Oct 2017 14:14:02 +0200 > > > > Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > > > > has_unmovable_pages > > > > > > > > Joonsoo has noticed that "mm: drop migrate type checks from > > > > has_unmovable_pages" would break CMA allocator because it relies on > > > > has_unmovable_pages returning false even for CMA pageblocks which in > > > > fact don't have to be movable: > > > > alloc_contig_range > > > > start_isolate_page_range > > > > set_migratetype_isolate > > > > has_unmovable_pages > > > > > > > > This is a result of the code sharing between CMA and memory hotplug > > > > while each one has a different idea of what has_unmovable_pages should > > > > return. This is unfortunate but fixing it properly would require a lot > > > > of code duplication. > > > > > > > > Fix the issue by introducing the requested migrate type argument > > > > and special case MIGRATE_CMA case where CMA page blocks are handled > > > > properly. This will work for memory hotplug because it requires > > > > MIGRATE_MOVABLE. > > > > > > Unfortunately, alloc_contig_range() can be called with > > > MIGRATE_MOVABLE so this patch cannot perfectly fix the problem. > > > > Yes, alloc_contig_range can be called with MIGRATE_MOVABLE but my > > understanding is that only CMA allocator really depends on this weird > > semantic and that does MIGRATE_CMA unconditionally. > > alloc_contig_range() could be called for partial pages in the > pageblock. With your patch, this case also fails unnecessarilly if the > other pages in the pageblock is pinned. Is this really the case for GB pages? Do we really want to mess those with CMA blocks and make those blocks basically unusable because GB pages are rarely (if at all migrateable)? > Until now, there is no user calling alloc_contig_range() with partial > pages except CMA allocator but API could support it. I disagree. If this is a CMA thing it should stay that way. The semantic is quite confusing already, please let's not make it even worse. > > > I did a more thinking and found that it's strange to check if there is > > > unmovable page in the pageblock during the set_migratetype_isolate(). > > > set_migratetype_isolate() should be just for setting the migratetype > > > of the pageblock. Checking other things should be done by another > > > place, for example, before calling the start_isolate_page_range() in > > > __offline_pages(). > > > > How do we guarantee the atomicity? > > What atomicity do you mean? Currently we are checking and isolating pages under zone lock. If we split that we are losing atomicity, aren't we. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 2017/10/20 10:13, Joonsoo Kim wrote: > On Thu, Oct 19, 2017 at 02:21:18PM +0200, Michal Hocko wrote: >> On Thu 19-10-17 10:20:41, Michal Hocko wrote: >>> On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: >>>> On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: >>>>> On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: >>> [...] >>>>>> Hello, >>>>>> >>>>>> This patch will break the CMA user. As you mentioned, CMA allocation >>>>>> itself isn't migrateable. So, after a single page is allocated through >>>>>> CMA allocation, has_unmovable_pages() will return true for this >>>>>> pageblock. Then, futher CMA allocation request to this pageblock will >>>>>> fail because it requires isolating the pageblock. >>>>> >>>>> Hmm, does this mean that the CMA allocation path depends on >>>>> has_unmovable_pages to return false here even though the memory is not >>>>> movable? This sounds really strange to me and kind of abuse of this >>>> >>>> Your understanding is correct. Perhaps, abuse or wrong function name. >>>> >>>>> function. Which path is that? Can we do the migrate type test theres? >>>> >>>> alloc_contig_range() -> start_isolate_page_range() -> >>>> set_migratetype_isolate() -> has_unmovable_pages() >>> >>> I see. It seems that the CMA and memory hotplug have a very different >>> view on what should happen during isolation. >>> >>>> We can add one argument, 'XXX' to set_migratetype_isolate() and change >>>> it to check migrate type rather than has_unmovable_pages() if 'XXX' is >>>> specified. >>> >>> Can we use the migratetype argument and do the special thing for >>> MIGRATE_CMA? Like the following diff? >> >> And with the full changelog. >> --- >> >From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 >> From: Michal Hocko <mhocko@suse.com> >> Date: Thu, 19 Oct 2017 14:14:02 +0200 >> Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in >> has_unmovable_pages >> >> Joonsoo has noticed that "mm: drop migrate type checks from >> has_unmovable_pages" would break CMA allocator because it relies on >> has_unmovable_pages returning false even for CMA pageblocks which in >> fact don't have to be movable: >> alloc_contig_range >> start_isolate_page_range >> set_migratetype_isolate >> has_unmovable_pages >> >> This is a result of the code sharing between CMA and memory hotplug >> while each one has a different idea of what has_unmovable_pages should >> return. This is unfortunate but fixing it properly would require a lot >> of code duplication. >> >> Fix the issue by introducing the requested migrate type argument >> and special case MIGRATE_CMA case where CMA page blocks are handled >> properly. This will work for memory hotplug because it requires >> MIGRATE_MOVABLE. > > Unfortunately, alloc_contig_range() can be called with > MIGRATE_MOVABLE so this patch cannot perfectly fix the problem. > > I did a more thinking and found that it's strange to check if there is > unmovable page in the pageblock during the set_migratetype_isolate(). > set_migratetype_isolate() should be just for setting the migratetype > of the pageblock. Checking other things should be done by another > place, for example, before calling the start_isolate_page_range() in > __offline_pages(). > > Thanks. > Hi Joonsoo, How about add a flag to skip or not has_unmovable_pages() in set_migratetype_isolate()? Something like the skip_hwpoisoned_pages. Thanks, Xishi Qiu > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Fri 20-10-17 15:22:14, Xishi Qiu wrote: > On 2017/10/20 10:13, Joonsoo Kim wrote: > > > On Thu, Oct 19, 2017 at 02:21:18PM +0200, Michal Hocko wrote: [...] > >> >From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > >> From: Michal Hocko <mhocko@suse.com> > >> Date: Thu, 19 Oct 2017 14:14:02 +0200 > >> Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > >> has_unmovable_pages > >> > >> Joonsoo has noticed that "mm: drop migrate type checks from > >> has_unmovable_pages" would break CMA allocator because it relies on > >> has_unmovable_pages returning false even for CMA pageblocks which in > >> fact don't have to be movable: > >> alloc_contig_range > >> start_isolate_page_range > >> set_migratetype_isolate > >> has_unmovable_pages > >> > >> This is a result of the code sharing between CMA and memory hotplug > >> while each one has a different idea of what has_unmovable_pages should > >> return. This is unfortunate but fixing it properly would require a lot > >> of code duplication. > >> > >> Fix the issue by introducing the requested migrate type argument > >> and special case MIGRATE_CMA case where CMA page blocks are handled > >> properly. This will work for memory hotplug because it requires > >> MIGRATE_MOVABLE. > > > > Unfortunately, alloc_contig_range() can be called with > > MIGRATE_MOVABLE so this patch cannot perfectly fix the problem. > > > > I did a more thinking and found that it's strange to check if there is > > unmovable page in the pageblock during the set_migratetype_isolate(). > > set_migratetype_isolate() should be just for setting the migratetype > > of the pageblock. Checking other things should be done by another > > place, for example, before calling the start_isolate_page_range() in > > __offline_pages(). > > > > Thanks. > > > > Hi Joonsoo, > > How about add a flag to skip or not has_unmovable_pages() in set_migratetype_isolate()? > Something like the skip_hwpoisoned_pages. I believe this is what Joonsoo was proposing actually. I cannot say I would like skip_hwpoisoned_pages and adding one more flag is just too ugly. So I would prefer to have something that would actually make sense from the semantic POV. If CMA really needs to work with partial CMA blocks then MIGRATE_CMA as an indicator sounds like the right way to go to me. But I am not a CMA expert so I might be missing some subtlety here. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Fri, Oct 20, 2017 at 09:02:20AM +0200, Michal Hocko wrote: > On Fri 20-10-17 15:50:14, Joonsoo Kim wrote: > > On Fri, Oct 20, 2017 at 07:59:22AM +0200, Michal Hocko wrote: > > > On Fri 20-10-17 11:13:29, Joonsoo Kim wrote: > > > > On Thu, Oct 19, 2017 at 02:21:18PM +0200, Michal Hocko wrote: > > > > > On Thu 19-10-17 10:20:41, Michal Hocko wrote: > > > > > > On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: > > > > > > > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > > > > > > > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > > > > > > [...] > > > > > > > > > Hello, > > > > > > > > > > > > > > > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > > > > > > > > itself isn't migrateable. So, after a single page is allocated through > > > > > > > > > CMA allocation, has_unmovable_pages() will return true for this > > > > > > > > > pageblock. Then, futher CMA allocation request to this pageblock will > > > > > > > > > fail because it requires isolating the pageblock. > > > > > > > > > > > > > > > > Hmm, does this mean that the CMA allocation path depends on > > > > > > > > has_unmovable_pages to return false here even though the memory is not > > > > > > > > movable? This sounds really strange to me and kind of abuse of this > > > > > > > > > > > > > > Your understanding is correct. Perhaps, abuse or wrong function name. > > > > > > > > > > > > > > > function. Which path is that? Can we do the migrate type test theres? > > > > > > > > > > > > > > alloc_contig_range() -> start_isolate_page_range() -> > > > > > > > set_migratetype_isolate() -> has_unmovable_pages() > > > > > > > > > > > > I see. It seems that the CMA and memory hotplug have a very different > > > > > > view on what should happen during isolation. > > > > > > > > > > > > > We can add one argument, 'XXX' to set_migratetype_isolate() and change > > > > > > > it to check migrate type rather than has_unmovable_pages() if 'XXX' is > > > > > > > specified. > > > > > > > > > > > > Can we use the migratetype argument and do the special thing for > > > > > > MIGRATE_CMA? Like the following diff? > > > > > > > > > > And with the full changelog. > > > > > --- > > > > > >From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > > > > > From: Michal Hocko <mhocko@suse.com> > > > > > Date: Thu, 19 Oct 2017 14:14:02 +0200 > > > > > Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > > > > > has_unmovable_pages > > > > > > > > > > Joonsoo has noticed that "mm: drop migrate type checks from > > > > > has_unmovable_pages" would break CMA allocator because it relies on > > > > > has_unmovable_pages returning false even for CMA pageblocks which in > > > > > fact don't have to be movable: > > > > > alloc_contig_range > > > > > start_isolate_page_range > > > > > set_migratetype_isolate > > > > > has_unmovable_pages > > > > > > > > > > This is a result of the code sharing between CMA and memory hotplug > > > > > while each one has a different idea of what has_unmovable_pages should > > > > > return. This is unfortunate but fixing it properly would require a lot > > > > > of code duplication. > > > > > > > > > > Fix the issue by introducing the requested migrate type argument > > > > > and special case MIGRATE_CMA case where CMA page blocks are handled > > > > > properly. This will work for memory hotplug because it requires > > > > > MIGRATE_MOVABLE. > > > > > > > > Unfortunately, alloc_contig_range() can be called with > > > > MIGRATE_MOVABLE so this patch cannot perfectly fix the problem. > > > > > > Yes, alloc_contig_range can be called with MIGRATE_MOVABLE but my > > > understanding is that only CMA allocator really depends on this weird > > > semantic and that does MIGRATE_CMA unconditionally. > > > > alloc_contig_range() could be called for partial pages in the > > pageblock. With your patch, this case also fails unnecessarilly if the > > other pages in the pageblock is pinned. > > Is this really the case for GB pages? Do we really want to mess those No, but, as I mentioned already, this API can be called with less pages. I know that there is no user with less pages at this moment but I cannot see any point to reduce this API's capability. > with CMA blocks and make those blocks basically unusable because GB > pages are rarely (if at all migrateable)? > > > Until now, there is no user calling alloc_contig_range() with partial > > pages except CMA allocator but API could support it. > > I disagree. If this is a CMA thing it should stay that way. The semantic > is quite confusing already, please let's not make it even worse. It is already used by other component. I'm not sure what is the confusing semantic you mentioned. I think that set_migratetype_isolate() has confusing semantic and should be fixed since making the pageblock isolated doesn't need to check if there is unmovable page or not. Do you think that set_migratetype_isolate() need to check it? If so, why? > > > > I did a more thinking and found that it's strange to check if there is > > > > unmovable page in the pageblock during the set_migratetype_isolate(). > > > > set_migratetype_isolate() should be just for setting the migratetype > > > > of the pageblock. Checking other things should be done by another > > > > place, for example, before calling the start_isolate_page_range() in > > > > __offline_pages(). > > > > > > How do we guarantee the atomicity? > > > > What atomicity do you mean? > > Currently we are checking and isolating pages under zone lock. If we > split that we are losing atomicity, aren't we. I think that it can be done easily. set_migratetype_isolate() { lock __set_migratetype_isolate(); unlock } set_migratetype_isolate_if_no_unmovable_pages() { lock if (has_unmovable_pages()) fail else __set_migratetype_isolate() unlock } Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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On Fri, Oct 20, 2017 at 10:17:00AM +0200, Michal Hocko wrote: > On Fri 20-10-17 15:22:14, Xishi Qiu wrote: > > On 2017/10/20 10:13, Joonsoo Kim wrote: > > > > > On Thu, Oct 19, 2017 at 02:21:18PM +0200, Michal Hocko wrote: > [...] > > >> >From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > > >> From: Michal Hocko <mhocko@suse.com> > > >> Date: Thu, 19 Oct 2017 14:14:02 +0200 > > >> Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > > >> has_unmovable_pages > > >> > > >> Joonsoo has noticed that "mm: drop migrate type checks from > > >> has_unmovable_pages" would break CMA allocator because it relies on > > >> has_unmovable_pages returning false even for CMA pageblocks which in > > >> fact don't have to be movable: > > >> alloc_contig_range > > >> start_isolate_page_range > > >> set_migratetype_isolate > > >> has_unmovable_pages > > >> > > >> This is a result of the code sharing between CMA and memory hotplug > > >> while each one has a different idea of what has_unmovable_pages should > > >> return. This is unfortunate but fixing it properly would require a lot > > >> of code duplication. > > >> > > >> Fix the issue by introducing the requested migrate type argument > > >> and special case MIGRATE_CMA case where CMA page blocks are handled > > >> properly. This will work for memory hotplug because it requires > > >> MIGRATE_MOVABLE. > > > > > > Unfortunately, alloc_contig_range() can be called with > > > MIGRATE_MOVABLE so this patch cannot perfectly fix the problem. > > > > > > I did a more thinking and found that it's strange to check if there is > > > unmovable page in the pageblock during the set_migratetype_isolate(). > > > set_migratetype_isolate() should be just for setting the migratetype > > > of the pageblock. Checking other things should be done by another > > > place, for example, before calling the start_isolate_page_range() in > > > __offline_pages(). > > > > > > Thanks. > > > > > > > Hi Joonsoo, > > > > How about add a flag to skip or not has_unmovable_pages() in set_migratetype_isolate()? > > Something like the skip_hwpoisoned_pages. > > I believe this is what Joonsoo was proposing actually. I cannot say I Yes, I initially suggested this idea but change my mind. Now, I think that problem is not in has_unmovable_pages() but in set_migratetype_isolate(). So different solution is needed. See my other reply to Michal. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Mon 23-10-17 14:23:09, Joonsoo Kim wrote: > On Fri, Oct 20, 2017 at 09:02:20AM +0200, Michal Hocko wrote: > > On Fri 20-10-17 15:50:14, Joonsoo Kim wrote: > > > On Fri, Oct 20, 2017 at 07:59:22AM +0200, Michal Hocko wrote: > > > > On Fri 20-10-17 11:13:29, Joonsoo Kim wrote: > > > > > On Thu, Oct 19, 2017 at 02:21:18PM +0200, Michal Hocko wrote: > > > > > > On Thu 19-10-17 10:20:41, Michal Hocko wrote: > > > > > > > On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: > > > > > > > > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > > > > > > > > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > > > > > > > [...] > > > > > > > > > > Hello, > > > > > > > > > > > > > > > > > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > > > > > > > > > itself isn't migrateable. So, after a single page is allocated through > > > > > > > > > > CMA allocation, has_unmovable_pages() will return true for this > > > > > > > > > > pageblock. Then, futher CMA allocation request to this pageblock will > > > > > > > > > > fail because it requires isolating the pageblock. > > > > > > > > > > > > > > > > > > Hmm, does this mean that the CMA allocation path depends on > > > > > > > > > has_unmovable_pages to return false here even though the memory is not > > > > > > > > > movable? This sounds really strange to me and kind of abuse of this > > > > > > > > > > > > > > > > Your understanding is correct. Perhaps, abuse or wrong function name. > > > > > > > > > > > > > > > > > function. Which path is that? Can we do the migrate type test theres? > > > > > > > > > > > > > > > > alloc_contig_range() -> start_isolate_page_range() -> > > > > > > > > set_migratetype_isolate() -> has_unmovable_pages() > > > > > > > > > > > > > > I see. It seems that the CMA and memory hotplug have a very different > > > > > > > view on what should happen during isolation. > > > > > > > > > > > > > > > We can add one argument, 'XXX' to set_migratetype_isolate() and change > > > > > > > > it to check migrate type rather than has_unmovable_pages() if 'XXX' is > > > > > > > > specified. > > > > > > > > > > > > > > Can we use the migratetype argument and do the special thing for > > > > > > > MIGRATE_CMA? Like the following diff? > > > > > > > > > > > > And with the full changelog. > > > > > > --- > > > > > > >From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > > > > > > From: Michal Hocko <mhocko@suse.com> > > > > > > Date: Thu, 19 Oct 2017 14:14:02 +0200 > > > > > > Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > > > > > > has_unmovable_pages > > > > > > > > > > > > Joonsoo has noticed that "mm: drop migrate type checks from > > > > > > has_unmovable_pages" would break CMA allocator because it relies on > > > > > > has_unmovable_pages returning false even for CMA pageblocks which in > > > > > > fact don't have to be movable: > > > > > > alloc_contig_range > > > > > > start_isolate_page_range > > > > > > set_migratetype_isolate > > > > > > has_unmovable_pages > > > > > > > > > > > > This is a result of the code sharing between CMA and memory hotplug > > > > > > while each one has a different idea of what has_unmovable_pages should > > > > > > return. This is unfortunate but fixing it properly would require a lot > > > > > > of code duplication. > > > > > > > > > > > > Fix the issue by introducing the requested migrate type argument > > > > > > and special case MIGRATE_CMA case where CMA page blocks are handled > > > > > > properly. This will work for memory hotplug because it requires > > > > > > MIGRATE_MOVABLE. > > > > > > > > > > Unfortunately, alloc_contig_range() can be called with > > > > > MIGRATE_MOVABLE so this patch cannot perfectly fix the problem. > > > > > > > > Yes, alloc_contig_range can be called with MIGRATE_MOVABLE but my > > > > understanding is that only CMA allocator really depends on this weird > > > > semantic and that does MIGRATE_CMA unconditionally. > > > > > > alloc_contig_range() could be called for partial pages in the > > > pageblock. With your patch, this case also fails unnecessarilly if the > > > other pages in the pageblock is pinned. > > > > Is this really the case for GB pages? Do we really want to mess those > > No, but, as I mentioned already, this API can be called with less > pages. I know that there is no user with less pages at this moment but > I cannot see any point to reduce this API's capability. I am still confused. So when exactly would you want to use this api for MIGRATE_MOVABLE and use a partial MIGRATE_CMA pageblock? > > with CMA blocks and make those blocks basically unusable because GB > > pages are rarely (if at all migrateable)? > > > > > Until now, there is no user calling alloc_contig_range() with partial > > > pages except CMA allocator but API could support it. > > > > I disagree. If this is a CMA thing it should stay that way. The semantic > > is quite confusing already, please let's not make it even worse. > > It is already used by other component. > > I'm not sure what is the confusing semantic you mentioned. I think > that set_migratetype_isolate() has confusing semantic and should be > fixed since making the pageblock isolated doesn't need to check if > there is unmovable page or not. Do you think that > set_migratetype_isolate() need to check it? If so, why? My intuitive understanding of set_migratetype_isolate is that it either suceeds and that means that the given pfn range can be isolated for the given type of allocation (be it movable or cma). No new pages will be allocated from this range to allow converging into a free range in a finit amount of time. At least this is how the hotplug code would like to use it and I suppose that the alloc_contig_range would like to guarantee the same to not rely on a fixed amount of migration attempts. > > > > > I did a more thinking and found that it's strange to check if there is > > > > > unmovable page in the pageblock during the set_migratetype_isolate(). > > > > > set_migratetype_isolate() should be just for setting the migratetype > > > > > of the pageblock. Checking other things should be done by another > > > > > place, for example, before calling the start_isolate_page_range() in > > > > > __offline_pages(). > > > > > > > > How do we guarantee the atomicity? > > > > > > What atomicity do you mean? > > > > Currently we are checking and isolating pages under zone lock. If we > > split that we are losing atomicity, aren't we. > > I think that it can be done easily. > > set_migratetype_isolate() { > lock > __set_migratetype_isolate(); > unlock > } > > set_migratetype_isolate_if_no_unmovable_pages() { > lock > if (has_unmovable_pages()) > fail > else > __set_migratetype_isolate() > unlock > } So you are essentially suggesting to split the API for alloc_contig_range and hotplug users? Care to send a patch? It is not like I would really love this but I would really like to have this issue addressed because I really do want all other patches which depend on this to be merged in the next release cycle. That being said, I would much rather see MIGRATE_CMA case special cased than duplicate the already confusing API but I will not insist of course. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . 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On Mon, Oct 23, 2017 at 10:10:09AM +0200, Michal Hocko wrote: > On Mon 23-10-17 14:23:09, Joonsoo Kim wrote: > > On Fri, Oct 20, 2017 at 09:02:20AM +0200, Michal Hocko wrote: > > > On Fri 20-10-17 15:50:14, Joonsoo Kim wrote: > > > > On Fri, Oct 20, 2017 at 07:59:22AM +0200, Michal Hocko wrote: > > > > > On Fri 20-10-17 11:13:29, Joonsoo Kim wrote: > > > > > > On Thu, Oct 19, 2017 at 02:21:18PM +0200, Michal Hocko wrote: > > > > > > > On Thu 19-10-17 10:20:41, Michal Hocko wrote: > > > > > > > > On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: > > > > > > > > > On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: > > > > > > > > > > On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: > > > > > > > > [...] > > > > > > > > > > > Hello, > > > > > > > > > > > > > > > > > > > > > > This patch will break the CMA user. As you mentioned, CMA allocation > > > > > > > > > > > itself isn't migrateable. So, after a single page is allocated through > > > > > > > > > > > CMA allocation, has_unmovable_pages() will return true for this > > > > > > > > > > > pageblock. Then, futher CMA allocation request to this pageblock will > > > > > > > > > > > fail because it requires isolating the pageblock. > > > > > > > > > > > > > > > > > > > > Hmm, does this mean that the CMA allocation path depends on > > > > > > > > > > has_unmovable_pages to return false here even though the memory is not > > > > > > > > > > movable? This sounds really strange to me and kind of abuse of this > > > > > > > > > > > > > > > > > > Your understanding is correct. Perhaps, abuse or wrong function name. > > > > > > > > > > > > > > > > > > > function. Which path is that? Can we do the migrate type test theres? > > > > > > > > > > > > > > > > > > alloc_contig_range() -> start_isolate_page_range() -> > > > > > > > > > set_migratetype_isolate() -> has_unmovable_pages() > > > > > > > > > > > > > > > > I see. It seems that the CMA and memory hotplug have a very different > > > > > > > > view on what should happen during isolation. > > > > > > > > > > > > > > > > > We can add one argument, 'XXX' to set_migratetype_isolate() and change > > > > > > > > > it to check migrate type rather than has_unmovable_pages() if 'XXX' is > > > > > > > > > specified. > > > > > > > > > > > > > > > > Can we use the migratetype argument and do the special thing for > > > > > > > > MIGRATE_CMA? Like the following diff? > > > > > > > > > > > > > > And with the full changelog. > > > > > > > --- > > > > > > > >From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > > > > > > > From: Michal Hocko <mhocko@suse.com> > > > > > > > Date: Thu, 19 Oct 2017 14:14:02 +0200 > > > > > > > Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > > > > > > > has_unmovable_pages > > > > > > > > > > > > > > Joonsoo has noticed that "mm: drop migrate type checks from > > > > > > > has_unmovable_pages" would break CMA allocator because it relies on > > > > > > > has_unmovable_pages returning false even for CMA pageblocks which in > > > > > > > fact don't have to be movable: > > > > > > > alloc_contig_range > > > > > > > start_isolate_page_range > > > > > > > set_migratetype_isolate > > > > > > > has_unmovable_pages > > > > > > > > > > > > > > This is a result of the code sharing between CMA and memory hotplug > > > > > > > while each one has a different idea of what has_unmovable_pages should > > > > > > > return. This is unfortunate but fixing it properly would require a lot > > > > > > > of code duplication. > > > > > > > > > > > > > > Fix the issue by introducing the requested migrate type argument > > > > > > > and special case MIGRATE_CMA case where CMA page blocks are handled > > > > > > > properly. This will work for memory hotplug because it requires > > > > > > > MIGRATE_MOVABLE. > > > > > > > > > > > > Unfortunately, alloc_contig_range() can be called with > > > > > > MIGRATE_MOVABLE so this patch cannot perfectly fix the problem. > > > > > > > > > > Yes, alloc_contig_range can be called with MIGRATE_MOVABLE but my > > > > > understanding is that only CMA allocator really depends on this weird > > > > > semantic and that does MIGRATE_CMA unconditionally. > > > > > > > > alloc_contig_range() could be called for partial pages in the > > > > pageblock. With your patch, this case also fails unnecessarilly if the > > > > other pages in the pageblock is pinned. > > > > > > Is this really the case for GB pages? Do we really want to mess those > > > > No, but, as I mentioned already, this API can be called with less > > pages. I know that there is no user with less pages at this moment but > > I cannot see any point to reduce this API's capability. > > I am still confused. So when exactly would you want to use this api for > MIGRATE_MOVABLE and use a partial MIGRATE_CMA pageblock? > > > > with CMA blocks and make those blocks basically unusable because GB > > > pages are rarely (if at all migrateable)? > > > > > > > Until now, there is no user calling alloc_contig_range() with partial > > > > pages except CMA allocator but API could support it. > > > > > > I disagree. If this is a CMA thing it should stay that way. The semantic > > > is quite confusing already, please let's not make it even worse. > > > > It is already used by other component. > > > > I'm not sure what is the confusing semantic you mentioned. I think > > that set_migratetype_isolate() has confusing semantic and should be > > fixed since making the pageblock isolated doesn't need to check if > > there is unmovable page or not. Do you think that > > set_migratetype_isolate() need to check it? If so, why? > > My intuitive understanding of set_migratetype_isolate is that it either > suceeds and that means that the given pfn range can be isolated for the > given type of allocation (be it movable or cma). No new pages will be > allocated from this range to allow converging into a free range in a > finit amount of time. At least this is how the hotplug code would like > to use it and I suppose that the alloc_contig_range would like to > guarantee the same to not rely on a fixed amount of migration attempts. Yes, alloc_contig_range() also want to guarantee the similar thing. Major difference between them is 'given pfn range'. memory hotplug works by pageblock unit but alloc_contig_range() doesn't. alloc_contig_range() works by the page unit. However, there is no easy way to isolate individual page so it uses pageblock isolation regardless of 'given pfn range'. In this case, checking movability of all pages on the pageblock would cause the problem as I mentioned before. > > > > > > > I did a more thinking and found that it's strange to check if there is > > > > > > unmovable page in the pageblock during the set_migratetype_isolate(). > > > > > > set_migratetype_isolate() should be just for setting the migratetype > > > > > > of the pageblock. Checking other things should be done by another > > > > > > place, for example, before calling the start_isolate_page_range() in > > > > > > __offline_pages(). > > > > > > > > > > How do we guarantee the atomicity? > > > > > > > > What atomicity do you mean? > > > > > > Currently we are checking and isolating pages under zone lock. If we > > > split that we are losing atomicity, aren't we. > > > > I think that it can be done easily. > > > > set_migratetype_isolate() { > > lock > > __set_migratetype_isolate(); > > unlock > > } > > > > set_migratetype_isolate_if_no_unmovable_pages() { > > lock > > if (has_unmovable_pages()) > > fail > > else > > __set_migratetype_isolate() > > unlock > > } > > So you are essentially suggesting to split the API for > alloc_contig_range and hotplug users? Care to send a patch? It is not > like I would really love this but I would really like to have this issue > addressed because I really do want all other patches which depend on > this to be merged in the next release cycle. > > That being said, I would much rather see MIGRATE_CMA case special cased > than duplicate the already confusing API but I will not insist of > course. Okay. I atteach the patch. Andrew, could you revert Michal's series and apply this patch first? Perhaps, Michal will resend his series on top of this one. Thanks. --------------->8-------------------
On Tue 24-10-17 13:44:23, Joonsoo Kim wrote: > On Mon, Oct 23, 2017 at 10:10:09AM +0200, Michal Hocko wrote: [...] > > My intuitive understanding of set_migratetype_isolate is that it either > > suceeds and that means that the given pfn range can be isolated for the > > given type of allocation (be it movable or cma). No new pages will be > > allocated from this range to allow converging into a free range in a > > finit amount of time. At least this is how the hotplug code would like > > to use it and I suppose that the alloc_contig_range would like to > > guarantee the same to not rely on a fixed amount of migration attempts. > > Yes, alloc_contig_range() also want to guarantee the similar thing. > Major difference between them is 'given pfn range'. memory hotplug > works by pageblock unit but alloc_contig_range() doesn't. > alloc_contig_range() works by the page unit. However, there is no easy > way to isolate individual page so it uses pageblock isolation > regardless of 'given pfn range'. I am still confused. So when is it safe to isolate a page from the CMA pageblock for something that is not a CMA allocation request? Don't we lose a CMA guanratee that way? [...] > > That being said, I would much rather see MIGRATE_CMA case special cased > > than duplicate the already confusing API but I will not insist of > > course. > > Okay. I atteach the patch. Andrew, could you revert Michal's series > and apply this patch first? Perhaps, Michal will resend his series on > top of this one. I am not convinced about this approach but I will not argue about the patch though. If this is seen as a right way forward, I will rebase my patches on top. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 10/24/2017 06:44 AM, Joonsoo Kim wrote: >>> I'm not sure what is the confusing semantic you mentioned. I think >>> that set_migratetype_isolate() has confusing semantic and should be >>> fixed since making the pageblock isolated doesn't need to check if >>> there is unmovable page or not. Do you think that >>> set_migratetype_isolate() need to check it? If so, why? >> >> My intuitive understanding of set_migratetype_isolate is that it either >> suceeds and that means that the given pfn range can be isolated for the >> given type of allocation (be it movable or cma). No new pages will be >> allocated from this range to allow converging into a free range in a >> finit amount of time. At least this is how the hotplug code would like >> to use it and I suppose that the alloc_contig_range would like to >> guarantee the same to not rely on a fixed amount of migration attempts. > > Yes, alloc_contig_range() also want to guarantee the similar thing. > Major difference between them is 'given pfn range'. memory hotplug > works by pageblock unit but alloc_contig_range() doesn't. > alloc_contig_range() works by the page unit. However, there is no easy > way to isolate individual page so it uses pageblock isolation > regardless of 'given pfn range'. In this case, checking movability of > all pages on the pageblock would cause the problem as I mentioned > before. I couldn't look too closely yet, but do I understand correctly that the *potential* problem (because as you say there are no such alloc_contig_range callers) you are describing is not newly introduced by Michal's series? Then his patch fixing the introduced regression should be enough for now, and further improvements could be posted on top, and not vice versa? Please don't take it wrong, I agree the current state is a bit of a mess and improvements are welcome. Also it seems to me that Michal is right, and there's nothing preventing alloc_contig_range() to allocate from CMA pageblocks for non-CMA purposes (likely not movable), and that should be also fixed? Vlastimil -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Tue 24-10-17 10:12:58, Vlastimil Babka wrote: > On 10/24/2017 06:44 AM, Joonsoo Kim wrote: > >>> I'm not sure what is the confusing semantic you mentioned. I think > >>> that set_migratetype_isolate() has confusing semantic and should be > >>> fixed since making the pageblock isolated doesn't need to check if > >>> there is unmovable page or not. Do you think that > >>> set_migratetype_isolate() need to check it? If so, why? > >> > >> My intuitive understanding of set_migratetype_isolate is that it either > >> suceeds and that means that the given pfn range can be isolated for the > >> given type of allocation (be it movable or cma). No new pages will be > >> allocated from this range to allow converging into a free range in a > >> finit amount of time. At least this is how the hotplug code would like > >> to use it and I suppose that the alloc_contig_range would like to > >> guarantee the same to not rely on a fixed amount of migration attempts. > > > > Yes, alloc_contig_range() also want to guarantee the similar thing. > > Major difference between them is 'given pfn range'. memory hotplug > > works by pageblock unit but alloc_contig_range() doesn't. > > alloc_contig_range() works by the page unit. However, there is no easy > > way to isolate individual page so it uses pageblock isolation > > regardless of 'given pfn range'. In this case, checking movability of > > all pages on the pageblock would cause the problem as I mentioned > > before. > > I couldn't look too closely yet, but do I understand correctly that the > *potential* problem (because as you say there are no such > alloc_contig_range callers) you are describing is not newly introduced > by Michal's series? Then his patch fixing the introduced regression > should be enough for now, and further improvements could be posted on > top, and not vice versa? Please don't take it wrong, I agree the current > state is a bit of a mess and improvements are welcome. Also it seems to > me that Michal is right, and there's nothing preventing > alloc_contig_range() to allocate from CMA pageblocks for non-CMA > purposes (likely not movable), and that should be also fixed? OK, it seems I understand Joonsoo's concern more now. And I agree with Vlastimil, that it is better to plug the immediate regression with a minimal patch and discuss general improvements of the pfn based allocator separatelly. There are more things to clear up there, including the proper API (alloc_contig_range is just too low level for anybody to use) as well as the MIGRATE_* flags usage (e.g. I am not really sure GB pages usage of MIGRATE_MOVABLE is really correct). alloc_contig_range looks like an internal CMA function which has been (ab)used for a different purpose to me rather than a well thought through interface. MAP_CONTIG discussion has shown some interest in an API for large allocations so I _believe_ we should think that through befire we grow more unexpected users. I am definitely willing to help there. Is that something you would agree with Joonsoo? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Tue, Oct 24, 2017 at 10:12:58AM +0200, Vlastimil Babka wrote: > On 10/24/2017 06:44 AM, Joonsoo Kim wrote: > >>> I'm not sure what is the confusing semantic you mentioned. I think > >>> that set_migratetype_isolate() has confusing semantic and should be > >>> fixed since making the pageblock isolated doesn't need to check if > >>> there is unmovable page or not. Do you think that > >>> set_migratetype_isolate() need to check it? If so, why? > >> > >> My intuitive understanding of set_migratetype_isolate is that it either > >> suceeds and that means that the given pfn range can be isolated for the > >> given type of allocation (be it movable or cma). No new pages will be > >> allocated from this range to allow converging into a free range in a > >> finit amount of time. At least this is how the hotplug code would like > >> to use it and I suppose that the alloc_contig_range would like to > >> guarantee the same to not rely on a fixed amount of migration attempts. > > > > Yes, alloc_contig_range() also want to guarantee the similar thing. > > Major difference between them is 'given pfn range'. memory hotplug > > works by pageblock unit but alloc_contig_range() doesn't. > > alloc_contig_range() works by the page unit. However, there is no easy > > way to isolate individual page so it uses pageblock isolation > > regardless of 'given pfn range'. In this case, checking movability of > > all pages on the pageblock would cause the problem as I mentioned > > before. > > I couldn't look too closely yet, but do I understand correctly that the > *potential* problem (because as you say there are no such > alloc_contig_range callers) you are describing is not newly introduced > by Michal's series? Then his patch fixing the introduced regression This potential problem exists there before Michal's series if the migratetype of the target pageblock isn't MIGRATE_MOVABLE or MIGRATE_CMA. However, his series enlarges this potential problem surface. It would be the problem now even if the migratetype of the target pageblock is MIGRATE_MOVABLE. > should be enough for now, and further improvements could be posted on > top, and not vice versa? Please don't take it wrong, I agree the current > state is a bit of a mess and improvements are welcome. Also it seems to I'm not very sensitive that which patch is applied first. I can do rebase. But, IMHO, correct applying order is my patch first and then Michal's series. Anyway, Michal, feel free to do what you think correct. > me that Michal is right, and there's nothing preventing > alloc_contig_range() to allocate from CMA pageblocks for non-CMA > purposes (likely not movable), and that should be also fixed? I noticed the problem you mentioned now and, yes, it should be fixed. My patch will naturally fixes this issue, too. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Thu 26-10-17 11:47:07, Joonsoo Kim wrote: > On Tue, Oct 24, 2017 at 10:12:58AM +0200, Vlastimil Babka wrote: > > On 10/24/2017 06:44 AM, Joonsoo Kim wrote: > > >>> I'm not sure what is the confusing semantic you mentioned. I think > > >>> that set_migratetype_isolate() has confusing semantic and should be > > >>> fixed since making the pageblock isolated doesn't need to check if > > >>> there is unmovable page or not. Do you think that > > >>> set_migratetype_isolate() need to check it? If so, why? > > >> > > >> My intuitive understanding of set_migratetype_isolate is that it either > > >> suceeds and that means that the given pfn range can be isolated for the > > >> given type of allocation (be it movable or cma). No new pages will be > > >> allocated from this range to allow converging into a free range in a > > >> finit amount of time. At least this is how the hotplug code would like > > >> to use it and I suppose that the alloc_contig_range would like to > > >> guarantee the same to not rely on a fixed amount of migration attempts. > > > > > > Yes, alloc_contig_range() also want to guarantee the similar thing. > > > Major difference between them is 'given pfn range'. memory hotplug > > > works by pageblock unit but alloc_contig_range() doesn't. > > > alloc_contig_range() works by the page unit. However, there is no easy > > > way to isolate individual page so it uses pageblock isolation > > > regardless of 'given pfn range'. In this case, checking movability of > > > all pages on the pageblock would cause the problem as I mentioned > > > before. > > > > I couldn't look too closely yet, but do I understand correctly that the > > *potential* problem (because as you say there are no such > > alloc_contig_range callers) you are describing is not newly introduced > > by Michal's series? Then his patch fixing the introduced regression > > This potential problem exists there before Michal's series if the > migratetype of the target pageblock isn't MIGRATE_MOVABLE or MIGRATE_CMA. > However, his series enlarges this potential problem surface. It > would be the problem now even if the migratetype of the target > pageblock is MIGRATE_MOVABLE. > > > should be enough for now, and further improvements could be posted on > > top, and not vice versa? Please don't take it wrong, I agree the current > > state is a bit of a mess and improvements are welcome. Also it seems to > > I'm not very sensitive that which patch is applied first. I can do > rebase. But, IMHO, correct applying order is my patch first and then > Michal's series. > > Anyway, Michal, feel free to do what you think correct. If you do not mind I would rather go with the simple patch first and then build on top of that. For two reasons 1) it documents the CMA requirement and 2) there do not seem to be any real users affected by the issue you are seeing right now. And 3) I really believe alloc_contig_range needs a deeper thought to be usable in more general contexts. > > me that Michal is right, and there's nothing preventing > > alloc_contig_range() to allocate from CMA pageblocks for non-CMA > > purposes (likely not movable), and that should be also fixed? > > I noticed the problem you mentioned now and, yes, it should be fixed. > My patch will naturally fixes this issue, too. I really do not see how. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On 10/19/2017 02:21 PM, Michal Hocko wrote: > On Thu 19-10-17 10:20:41, Michal Hocko wrote: >> On Thu 19-10-17 16:33:56, Joonsoo Kim wrote: >>> On Thu, Oct 19, 2017 at 09:15:03AM +0200, Michal Hocko wrote: >>>> On Thu 19-10-17 11:51:11, Joonsoo Kim wrote: >> [...] >>>>> Hello, >>>>> >>>>> This patch will break the CMA user. As you mentioned, CMA allocation >>>>> itself isn't migrateable. So, after a single page is allocated through >>>>> CMA allocation, has_unmovable_pages() will return true for this >>>>> pageblock. Then, futher CMA allocation request to this pageblock will >>>>> fail because it requires isolating the pageblock. >>>> >>>> Hmm, does this mean that the CMA allocation path depends on >>>> has_unmovable_pages to return false here even though the memory is not >>>> movable? This sounds really strange to me and kind of abuse of this >>> >>> Your understanding is correct. Perhaps, abuse or wrong function name. >>> >>>> function. Which path is that? Can we do the migrate type test theres? >>> >>> alloc_contig_range() -> start_isolate_page_range() -> >>> set_migratetype_isolate() -> has_unmovable_pages() >> >> I see. It seems that the CMA and memory hotplug have a very different >> view on what should happen during isolation. >> >>> We can add one argument, 'XXX' to set_migratetype_isolate() and change >>> it to check migrate type rather than has_unmovable_pages() if 'XXX' is >>> specified. >> >> Can we use the migratetype argument and do the special thing for >> MIGRATE_CMA? Like the following diff? > > And with the full changelog. > --- > From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@suse.com> > Date: Thu, 19 Oct 2017 14:14:02 +0200 > Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > has_unmovable_pages > > Joonsoo has noticed that "mm: drop migrate type checks from > has_unmovable_pages" would break CMA allocator because it relies on > has_unmovable_pages returning false even for CMA pageblocks which in > fact don't have to be movable: > alloc_contig_range > start_isolate_page_range > set_migratetype_isolate > has_unmovable_pages > > This is a result of the code sharing between CMA and memory hotplug > while each one has a different idea of what has_unmovable_pages should > return. This is unfortunate but fixing it properly would require a lot > of code duplication. > > Fix the issue by introducing the requested migrate type argument > and special case MIGRATE_CMA case where CMA page blocks are handled > properly. This will work for memory hotplug because it requires > MIGRATE_MOVABLE. > > Reported-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> > Signed-off-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > include/linux/page-isolation.h | 2 +- > mm/page_alloc.c | 12 +++++++++++- > mm/page_isolation.c | 10 +++++----- > 3 files changed, 17 insertions(+), 7 deletions(-) > > diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h > index d4cd2014fa6f..fa9db0c7b54e 100644 > --- a/include/linux/page-isolation.h > +++ b/include/linux/page-isolation.h > @@ -30,7 +30,7 @@ static inline bool is_migrate_isolate(int migratetype) > #endif > > bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > - bool skip_hwpoisoned_pages); > + int migratetype, bool skip_hwpoisoned_pages); > void set_pageblock_migratetype(struct page *page, int migratetype); > int move_freepages_block(struct zone *zone, struct page *page, > int migratetype, int *num_movable); > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 5b4d85ae445c..259aeb22462f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7344,6 +7344,7 @@ void *__init alloc_large_system_hash(const char *tablename, > * race condition. So you can't expect this function should be exact. > */ > bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > + int migratetype, > bool skip_hwpoisoned_pages) > { > unsigned long pfn, iter, found; > @@ -7356,6 +7357,15 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > if (zone_idx(zone) == ZONE_MOVABLE) > return false; > > + /* > + * CMA allocations (alloc_contig_range) really need to mark isolate > + * CMA pageblocks even when they are not movable in fact so consider > + * them movable here. > + */ > + if (is_migrate_cma(migratetype) && > + is_migrate_cma(get_pageblock_migratetype(page))) > + return false; > + > pfn = page_to_pfn(page); > for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { > unsigned long check = pfn + iter; > @@ -7441,7 +7451,7 @@ bool is_pageblock_removable_nolock(struct page *page) > if (!zone_spans_pfn(zone, pfn)) > return false; > > - return !has_unmovable_pages(zone, page, 0, true); > + return !has_unmovable_pages(zone, page, 0, MIGRATE_MOVABLE, true); > } > > #if (defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || defined(CONFIG_CMA) > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index 757410d9f758..8616f5332c77 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -14,7 +14,7 @@ > #define CREATE_TRACE_POINTS > #include <trace/events/page_isolation.h> > > -static int set_migratetype_isolate(struct page *page, > +static int set_migratetype_isolate(struct page *page, int migratetype, > bool skip_hwpoisoned_pages) > { > struct zone *zone; > @@ -51,7 +51,7 @@ static int set_migratetype_isolate(struct page *page, > * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself. > * We just check MOVABLE pages. > */ > - if (!has_unmovable_pages(zone, page, arg.pages_found, > + if (!has_unmovable_pages(zone, page, arg.pages_found, migratetype, > skip_hwpoisoned_pages)) > ret = 0; > > @@ -63,14 +63,14 @@ static int set_migratetype_isolate(struct page *page, > out: > if (!ret) { > unsigned long nr_pages; > - int migratetype = get_pageblock_migratetype(page); > + int mt = get_pageblock_migratetype(page); > > set_pageblock_migratetype(page, MIGRATE_ISOLATE); > zone->nr_isolate_pageblock++; > nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE, > NULL); > > - __mod_zone_freepage_state(zone, -nr_pages, migratetype); > + __mod_zone_freepage_state(zone, -nr_pages, mt); > } > > spin_unlock_irqrestore(&zone->lock, flags); > @@ -182,7 +182,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, > pfn += pageblock_nr_pages) { > page = __first_valid_page(pfn, pageblock_nr_pages); > if (page && > - set_migratetype_isolate(page, skip_hwpoisoned_pages)) { > + set_migratetype_isolate(page, migratetype, skip_hwpoisoned_pages)) { > undo_pfn = pfn; > goto undo; > } > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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On Thu 19-10-17 14:21:18, Michal Hocko wrote: [...] > From 8cbd811d741f5dd93d1b21bb3ef94482a4d0bd32 Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@suse.com> > Date: Thu, 19 Oct 2017 14:14:02 +0200 > Subject: [PATCH] mm: distinguish CMA and MOVABLE isolation in > has_unmovable_pages > > Joonsoo has noticed that "mm: drop migrate type checks from > has_unmovable_pages" would break CMA allocator because it relies on > has_unmovable_pages returning false even for CMA pageblocks which in > fact don't have to be movable: > alloc_contig_range > start_isolate_page_range > set_migratetype_isolate > has_unmovable_pages > > This is a result of the code sharing between CMA and memory hotplug > while each one has a different idea of what has_unmovable_pages should > return. This is unfortunate but fixing it properly would require a lot > of code duplication. > > Fix the issue by introducing the requested migrate type argument > and special case MIGRATE_CMA case where CMA page blocks are handled > properly. This will work for memory hotplug because it requires > MIGRATE_MOVABLE. > > Reported-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> > Signed-off-by: Michal Hocko <mhocko@suse.com> > --- Andrew, could you add this one to the bundle as well? After mm-drop-migrate-type-checks-from-has_unmovable_pages.patch, please. Joonsoo would like to see a larger change in this area [1] but I think we need to think those much more through [2] and Joonsoo agreed to take the simpler patch first [3]. Thanks! [1] http://lkml.kernel.org/r/20171024044423.GA31424@js1304-P5Q-DELUXE [2] http://lkml.kernel.org/r/20171024122526.3kmabkcbmj4johli@dhcp22.suse.cz [3] http://lkml.kernel.org/r/20171026024707.GA11791@js1304-P5Q-DELUXE > include/linux/page-isolation.h | 2 +- > mm/page_alloc.c | 12 +++++++++++- > mm/page_isolation.c | 10 +++++----- > 3 files changed, 17 insertions(+), 7 deletions(-) > > diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h > index d4cd2014fa6f..fa9db0c7b54e 100644 > --- a/include/linux/page-isolation.h > +++ b/include/linux/page-isolation.h > @@ -30,7 +30,7 @@ static inline bool is_migrate_isolate(int migratetype) > #endif > > bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > - bool skip_hwpoisoned_pages); > + int migratetype, bool skip_hwpoisoned_pages); > void set_pageblock_migratetype(struct page *page, int migratetype); > int move_freepages_block(struct zone *zone, struct page *page, > int migratetype, int *num_movable); > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 5b4d85ae445c..259aeb22462f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7344,6 +7344,7 @@ void *__init alloc_large_system_hash(const char *tablename, > * race condition. So you can't expect this function should be exact. > */ > bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > + int migratetype, > bool skip_hwpoisoned_pages) > { > unsigned long pfn, iter, found; > @@ -7356,6 +7357,15 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > if (zone_idx(zone) == ZONE_MOVABLE) > return false; > > + /* > + * CMA allocations (alloc_contig_range) really need to mark isolate > + * CMA pageblocks even when they are not movable in fact so consider > + * them movable here. > + */ > + if (is_migrate_cma(migratetype) && > + is_migrate_cma(get_pageblock_migratetype(page))) > + return false; > + > pfn = page_to_pfn(page); > for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { > unsigned long check = pfn + iter; > @@ -7441,7 +7451,7 @@ bool is_pageblock_removable_nolock(struct page *page) > if (!zone_spans_pfn(zone, pfn)) > return false; > > - return !has_unmovable_pages(zone, page, 0, true); > + return !has_unmovable_pages(zone, page, 0, MIGRATE_MOVABLE, true); > } > > #if (defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || defined(CONFIG_CMA) > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index 757410d9f758..8616f5332c77 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -14,7 +14,7 @@ > #define CREATE_TRACE_POINTS > #include <trace/events/page_isolation.h> > > -static int set_migratetype_isolate(struct page *page, > +static int set_migratetype_isolate(struct page *page, int migratetype, > bool skip_hwpoisoned_pages) > { > struct zone *zone; > @@ -51,7 +51,7 @@ static int set_migratetype_isolate(struct page *page, > * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself. > * We just check MOVABLE pages. > */ > - if (!has_unmovable_pages(zone, page, arg.pages_found, > + if (!has_unmovable_pages(zone, page, arg.pages_found, migratetype, > skip_hwpoisoned_pages)) > ret = 0; > > @@ -63,14 +63,14 @@ static int set_migratetype_isolate(struct page *page, > out: > if (!ret) { > unsigned long nr_pages; > - int migratetype = get_pageblock_migratetype(page); > + int mt = get_pageblock_migratetype(page); > > set_pageblock_migratetype(page, MIGRATE_ISOLATE); > zone->nr_isolate_pageblock++; > nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE, > NULL); > > - __mod_zone_freepage_state(zone, -nr_pages, migratetype); > + __mod_zone_freepage_state(zone, -nr_pages, mt); > } > > spin_unlock_irqrestore(&zone->lock, flags); > @@ -182,7 +182,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, > pfn += pageblock_nr_pages) { > page = __first_valid_page(pfn, pageblock_nr_pages); > if (page && > - set_migratetype_isolate(page, skip_hwpoisoned_pages)) { > + set_migratetype_isolate(page, migratetype, skip_hwpoisoned_pages)) { > undo_pfn = pfn; > goto undo; > } > -- > 2.14.2 > > -- > Michal Hocko > SUSE Labs -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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