* Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY
2019-03-20 8:07 [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY Baoquan He
@ 2019-03-20 8:46 ` Michal Hocko
2019-03-20 9:06 ` Baoquan He
2019-03-20 12:27 ` Oscar Salvador
` (2 subsequent siblings)
3 siblings, 1 reply; 10+ messages in thread
From: Michal Hocko @ 2019-03-20 8:46 UTC (permalink / raw)
To: Baoquan He; +Cc: linux-kernel, akpm, osalvador, david, richard.weiyang, rppt
On Wed 20-03-19 16:07:32, Baoquan He wrote:
> In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
> is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
> enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
> and CONFIG_ZONE_DMA is also optional.
>
> Replace it with ZONE_HIGHMEM.
N*MEMORY is confusing as hell but I am really curious whether we have
ZONE_DMA32 and ZONE_HIGMEM together?
That being said N.*MEMORY is intended to check for nodes rather than
zones so the patch looks good to me but I think the above explanation is
misleading and will add even more mud to the picture when somebody tries
to understand what the heck is going on here.
> Fixes: 8efe33f40f3e ("mm/memory_hotplug.c: simplify node_states_check_changes_online")
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
> mm/memory_hotplug.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 6b05576fb4ec..09911d34a3be 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -712,7 +712,7 @@ static void node_states_check_changes_online(unsigned long nr_pages,
> if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY))
> arg->status_change_nid_normal = nid;
> #ifdef CONFIG_HIGHMEM
> - if (zone_idx(zone) <= N_HIGH_MEMORY && !node_state(nid, N_HIGH_MEMORY))
> + if (zone_idx(zone) <= ZONE_HIGHMEM && !node_state(nid, N_HIGH_MEMORY))
> arg->status_change_nid_high = nid;
> #endif
> }
> --
> 2.17.2
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY
2019-03-20 8:46 ` Michal Hocko
@ 2019-03-20 9:06 ` Baoquan He
2019-03-20 9:11 ` David Hildenbrand
2019-03-20 9:37 ` Michal Hocko
0 siblings, 2 replies; 10+ messages in thread
From: Baoquan He @ 2019-03-20 9:06 UTC (permalink / raw)
To: Michal Hocko; +Cc: linux-kernel, akpm, osalvador, david, richard.weiyang, rppt
On 03/20/19 at 09:46am, Michal Hocko wrote:
> On Wed 20-03-19 16:07:32, Baoquan He wrote:
> > In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> > to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> > always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
> > is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
> > enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
> > and CONFIG_ZONE_DMA is also optional.
> >
> > Replace it with ZONE_HIGHMEM.
>
> N*MEMORY is confusing as hell but I am really curious whether we have
> ZONE_DMA32 and ZONE_HIGMEM together?
Not sure. AFAIK, on x86_32 it can't be.
>
> That being said N.*MEMORY is intended to check for nodes rather than
> zones so the patch looks good to me but I think the above explanation is
> misleading and will add even more mud to the picture when somebody tries
> to understand what the heck is going on here.
Yes, agree. I also thought this again after I sent out patch, feel log is not
good. As you said, they are value of enum node_states and enum zone_type
separately.
How about this:
~~~
In function node_states_check_changes_online(), N_HIGH_MEMORY is used
to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
is to mark the memory state of node. Here zone index is checked, which
should be compared with 'ZONE_HIGHMEM' accordingly.
Replace it with ZONE_HIGHMEM.
~~~
>
> > Fixes: 8efe33f40f3e ("mm/memory_hotplug.c: simplify node_states_check_changes_online")
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> > mm/memory_hotplug.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index 6b05576fb4ec..09911d34a3be 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -712,7 +712,7 @@ static void node_states_check_changes_online(unsigned long nr_pages,
> > if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY))
> > arg->status_change_nid_normal = nid;
> > #ifdef CONFIG_HIGHMEM
> > - if (zone_idx(zone) <= N_HIGH_MEMORY && !node_state(nid, N_HIGH_MEMORY))
> > + if (zone_idx(zone) <= ZONE_HIGHMEM && !node_state(nid, N_HIGH_MEMORY))
> > arg->status_change_nid_high = nid;
> > #endif
> > }
> > --
> > 2.17.2
>
> --
> Michal Hocko
> SUSE Labs
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY
2019-03-20 9:06 ` Baoquan He
@ 2019-03-20 9:11 ` David Hildenbrand
2019-03-20 9:29 ` Baoquan He
2019-03-20 9:37 ` Michal Hocko
1 sibling, 1 reply; 10+ messages in thread
From: David Hildenbrand @ 2019-03-20 9:11 UTC (permalink / raw)
To: Baoquan He, Michal Hocko
Cc: linux-kernel, akpm, osalvador, richard.weiyang, rppt
On 20.03.19 10:06, Baoquan He wrote:
> On 03/20/19 at 09:46am, Michal Hocko wrote:
>> On Wed 20-03-19 16:07:32, Baoquan He wrote:
>>> In function node_states_check_changes_online(), N_HIGH_MEMORY is used
>>> to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
>>> always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
>>> is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
>>> enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
>>> and CONFIG_ZONE_DMA is also optional.
>>>
>>> Replace it with ZONE_HIGHMEM.
>>
>> N*MEMORY is confusing as hell but I am really curious whether we have
>> ZONE_DMA32 and ZONE_HIGMEM together?
>
> Not sure. AFAIK, on x86_32 it can't be.
>
>>
>> That being said N.*MEMORY is intended to check for nodes rather than
>> zones so the patch looks good to me but I think the above explanation is
>> misleading and will add even more mud to the picture when somebody tries
>> to understand what the heck is going on here.
>
> Yes, agree. I also thought this again after I sent out patch, feel log is not
> good. As you said, they are value of enum node_states and enum zone_type
> separately.
>
> How about this:
>
> ~~~
> In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> is to mark the memory state of node. Here zone index is checked, which
> should be compared with 'ZONE_HIGHMEM' accordingly.
>
> Replace it with ZONE_HIGHMEM.
Reviewed-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY
2019-03-20 9:11 ` David Hildenbrand
@ 2019-03-20 9:29 ` Baoquan He
0 siblings, 0 replies; 10+ messages in thread
From: Baoquan He @ 2019-03-20 9:29 UTC (permalink / raw)
To: Michal Hocko, David Hildenbrand
Cc: linux-kernel, akpm, osalvador, richard.weiyang, rppt
On 03/20/19 at 10:11am, David Hildenbrand wrote:
> On 20.03.19 10:06, Baoquan He wrote:
> > On 03/20/19 at 09:46am, Michal Hocko wrote:
> >> On Wed 20-03-19 16:07:32, Baoquan He wrote:
> >>> In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> >>> to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> >>> always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
> >>> is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
> >>> enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
> >>> and CONFIG_ZONE_DMA is also optional.
> >>>
> >>> Replace it with ZONE_HIGHMEM.
> >>
> >> N*MEMORY is confusing as hell but I am really curious whether we have
> >> ZONE_DMA32 and ZONE_HIGMEM together?
> >
> > Not sure. AFAIK, on x86_32 it can't be.
> >
> >>
> >> That being said N.*MEMORY is intended to check for nodes rather than
> >> zones so the patch looks good to me but I think the above explanation is
> >> misleading and will add even more mud to the picture when somebody tries
> >> to understand what the heck is going on here.
> >
> > Yes, agree. I also thought this again after I sent out patch, feel log is not
> > good. As you said, they are value of enum node_states and enum zone_type
> > separately.
> >
> > How about this:
> >
> > ~~~
> > In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> > to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> > is to mark the memory state of node. Here zone index is checked, which
> > should be compared with 'ZONE_HIGHMEM' accordingly.
> >
> > Replace it with ZONE_HIGHMEM.
>
> Reviewed-by: David Hildenbrand <david@redhat.com>
Thanks, both. Will use this log and repost.
Thanks
Baoquan
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY
2019-03-20 9:06 ` Baoquan He
2019-03-20 9:11 ` David Hildenbrand
@ 2019-03-20 9:37 ` Michal Hocko
1 sibling, 0 replies; 10+ messages in thread
From: Michal Hocko @ 2019-03-20 9:37 UTC (permalink / raw)
To: Baoquan He; +Cc: linux-kernel, akpm, osalvador, david, richard.weiyang, rppt
On Wed 20-03-19 17:06:24, Baoquan He wrote:
> On 03/20/19 at 09:46am, Michal Hocko wrote:
> > On Wed 20-03-19 16:07:32, Baoquan He wrote:
> > > In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> > > to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> > > always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
> > > is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
> > > enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
> > > and CONFIG_ZONE_DMA is also optional.
> > >
> > > Replace it with ZONE_HIGHMEM.
> >
> > N*MEMORY is confusing as hell but I am really curious whether we have
> > ZONE_DMA32 and ZONE_HIGMEM together?
>
> Not sure. AFAIK, on x86_32 it can't be.
>
> >
> > That being said N.*MEMORY is intended to check for nodes rather than
> > zones so the patch looks good to me but I think the above explanation is
> > misleading and will add even more mud to the picture when somebody tries
> > to understand what the heck is going on here.
>
> Yes, agree. I also thought this again after I sent out patch, feel log is not
> good. As you said, they are value of enum node_states and enum zone_type
> separately.
>
> How about this:
>
> ~~~
> In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> is to mark the memory state of node. Here zone index is checked, which
> should be compared with 'ZONE_HIGHMEM' accordingly.
>
> Replace it with ZONE_HIGHMEM.
OK, this is better. Thanks!
Feel free to stamp the patch with
Acked-by: Michal Hocko <mhocko@suse.com>
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY
2019-03-20 8:07 [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY Baoquan He
2019-03-20 8:46 ` Michal Hocko
@ 2019-03-20 12:27 ` Oscar Salvador
2019-03-20 12:28 ` Oscar Salvador
2019-03-20 19:12 ` Andrew Morton
3 siblings, 0 replies; 10+ messages in thread
From: Oscar Salvador @ 2019-03-20 12:27 UTC (permalink / raw)
To: Baoquan He; +Cc: linux-kernel, akpm, mhocko, david, richard.weiyang, rppt
On Wed, Mar 20, 2019 at 04:07:32PM +0800, Baoquan He wrote:
> In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
> is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
> enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
> and CONFIG_ZONE_DMA is also optional.
>
> Replace it with ZONE_HIGHMEM.
>
> Fixes: 8efe33f40f3e ("mm/memory_hotplug.c: simplify node_states_check_changes_online")
> Signed-off-by: Baoquan He <bhe@redhat.com>
Yeah, that was an oversight.
I got it right in node_states_check_changes_offline but not here.
Thanks to catch this.
Reviewed-by: Oscar Salvador <osalvador@suse.de>
> ---
> mm/memory_hotplug.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 6b05576fb4ec..09911d34a3be 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -712,7 +712,7 @@ static void node_states_check_changes_online(unsigned long nr_pages,
> if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY))
> arg->status_change_nid_normal = nid;
> #ifdef CONFIG_HIGHMEM
> - if (zone_idx(zone) <= N_HIGH_MEMORY && !node_state(nid, N_HIGH_MEMORY))
> + if (zone_idx(zone) <= ZONE_HIGHMEM && !node_state(nid, N_HIGH_MEMORY))
> arg->status_change_nid_high = nid;
> #endif
> }
> --
> 2.17.2
>
--
Oscar Salvador
SUSE L3
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY
2019-03-20 8:07 [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY Baoquan He
2019-03-20 8:46 ` Michal Hocko
2019-03-20 12:27 ` Oscar Salvador
@ 2019-03-20 12:28 ` Oscar Salvador
2019-03-20 19:12 ` Andrew Morton
3 siblings, 0 replies; 10+ messages in thread
From: Oscar Salvador @ 2019-03-20 12:28 UTC (permalink / raw)
To: Baoquan He; +Cc: linux-kernel, akpm, mhocko, david, richard.weiyang, rppt
On Wed, Mar 20, 2019 at 04:07:32PM +0800, Baoquan He wrote:
> In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
> is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
> enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
> and CONFIG_ZONE_DMA is also optional.
>
> Replace it with ZONE_HIGHMEM.
>
> Fixes: 8efe33f40f3e ("mm/memory_hotplug.c: simplify node_states_check_changes_online")
> Signed-off-by: Baoquan He <bhe@redhat.com>
I think you forgot linux-mm list
> ---
> mm/memory_hotplug.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 6b05576fb4ec..09911d34a3be 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -712,7 +712,7 @@ static void node_states_check_changes_online(unsigned long nr_pages,
> if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY))
> arg->status_change_nid_normal = nid;
> #ifdef CONFIG_HIGHMEM
> - if (zone_idx(zone) <= N_HIGH_MEMORY && !node_state(nid, N_HIGH_MEMORY))
> + if (zone_idx(zone) <= ZONE_HIGHMEM && !node_state(nid, N_HIGH_MEMORY))
> arg->status_change_nid_high = nid;
> #endif
> }
> --
> 2.17.2
>
--
Oscar Salvador
SUSE L3
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY
2019-03-20 8:07 [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY Baoquan He
` (2 preceding siblings ...)
2019-03-20 12:28 ` Oscar Salvador
@ 2019-03-20 19:12 ` Andrew Morton
2019-03-20 19:53 ` Michal Hocko
3 siblings, 1 reply; 10+ messages in thread
From: Andrew Morton @ 2019-03-20 19:12 UTC (permalink / raw)
To: Baoquan He
Cc: linux-kernel, osalvador, mhocko, david, richard.weiyang, rppt, linux-mm
On Wed, 20 Mar 2019 16:07:32 +0800 Baoquan He <bhe@redhat.com> wrote:
> In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
> is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
> enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
> and CONFIG_ZONE_DMA is also optional.
>
> Replace it with ZONE_HIGHMEM.
>
> Fixes: 8efe33f40f3e ("mm/memory_hotplug.c: simplify node_states_check_changes_online")
What are the runtime effects of this change?
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -712,7 +712,7 @@ static void node_states_check_changes_online(unsigned long nr_pages,
> if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY))
> arg->status_change_nid_normal = nid;
> #ifdef CONFIG_HIGHMEM
> - if (zone_idx(zone) <= N_HIGH_MEMORY && !node_state(nid, N_HIGH_MEMORY))
> + if (zone_idx(zone) <= ZONE_HIGHMEM && !node_state(nid, N_HIGH_MEMORY))
> arg->status_change_nid_high = nid;
> #endif
> }
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY
2019-03-20 19:12 ` Andrew Morton
@ 2019-03-20 19:53 ` Michal Hocko
0 siblings, 0 replies; 10+ messages in thread
From: Michal Hocko @ 2019-03-20 19:53 UTC (permalink / raw)
To: Andrew Morton
Cc: Baoquan He, linux-kernel, osalvador, david, richard.weiyang,
rppt, linux-mm
On Wed 20-03-19 12:12:09, Andrew Morton wrote:
> On Wed, 20 Mar 2019 16:07:32 +0800 Baoquan He <bhe@redhat.com> wrote:
>
> > In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> > to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> > always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
> > is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
> > enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
> > and CONFIG_ZONE_DMA is also optional.
> >
> > Replace it with ZONE_HIGHMEM.
> >
> > Fixes: 8efe33f40f3e ("mm/memory_hotplug.c: simplify node_states_check_changes_online")
>
> What are the runtime effects of this change?
There shouldn't be none. The code is just messy. The newer changelog
should make it more clear I believe.
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -712,7 +712,7 @@ static void node_states_check_changes_online(unsigned long nr_pages,
> > if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY))
> > arg->status_change_nid_normal = nid;
> > #ifdef CONFIG_HIGHMEM
> > - if (zone_idx(zone) <= N_HIGH_MEMORY && !node_state(nid, N_HIGH_MEMORY))
> > + if (zone_idx(zone) <= ZONE_HIGHMEM && !node_state(nid, N_HIGH_MEMORY))
> > arg->status_change_nid_high = nid;
> > #endif
> > }
>
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 10+ messages in thread