From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, Michael Ellerman <mpe@ellerman.id.au>,
Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Reza Arbab <arbab@linux.vnet.ibm.com>,
Yasuaki Ishimatsu <yasu.isimatu@gmail.com>,
qiuxishi@huawei.com, Igor Mammedov <imammedo@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages
Date: Thu, 19 Oct 2017 16:33:56 +0900 [thread overview]
Message-ID: <20171019073355.GA4486@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <20171019071503.e7w5fo35lsq6ca54@dhcp22.suse.cz>
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.
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next prev parent reply other threads:[~2017-10-19 7:30 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-18 7:08 [PATCH v2 0/2] mm, memory_hotplug: redefine memory offline retry logic Michal Hocko
2017-09-18 7:08 ` [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early Michal Hocko
2017-10-10 12:05 ` Michael Ellerman
2017-10-10 12:27 ` Michal Hocko
2017-10-11 2:37 ` Michael Ellerman
2017-10-11 5:19 ` Michael Ellerman
2017-10-11 14:05 ` Anshuman Khandual
2017-10-11 14:16 ` Michal Hocko
2017-10-11 6:51 ` Michal Hocko
2017-10-11 8:04 ` Vlastimil Babka
2017-10-11 8:13 ` Michal Hocko
2017-10-11 11:17 ` Vlastimil Babka
2017-10-11 11:24 ` Michal Hocko
2017-10-13 11:42 ` Michael Ellerman
2017-10-13 11:58 ` Michal Hocko
2017-10-13 12:00 ` [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Michal Hocko
2017-10-13 12:00 ` [PATCH 2/2] mm, page_alloc: fail has_unmovable_pages when seeing reserved pages Michal Hocko
2017-10-13 12:04 ` Vlastimil Babka
2017-10-13 12:07 ` Michal Hocko
2017-10-17 13:03 ` Vlastimil Babka
2017-10-17 11:41 ` [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Michael Ellerman
2017-10-17 12:03 ` Michal Hocko
2017-10-17 13:02 ` Vlastimil Babka
2017-10-19 2:51 ` Joonsoo Kim
2017-10-19 7:15 ` Michal Hocko
2017-10-19 7:33 ` Joonsoo Kim [this message]
2017-10-19 8:20 ` Michal Hocko
2017-10-19 12:21 ` Michal Hocko
2017-10-20 2:13 ` Joonsoo Kim
2017-10-20 5:59 ` Michal Hocko
2017-10-20 6:50 ` Joonsoo Kim
2017-10-20 7:02 ` Michal Hocko
2017-10-23 5:23 ` Joonsoo Kim
2017-10-23 8:10 ` Michal Hocko
2017-10-24 4:44 ` Joonsoo Kim
2017-10-24 7:44 ` Michal Hocko
2017-10-24 8:12 ` Vlastimil Babka
2017-10-24 12:25 ` Michal Hocko
2017-10-26 2:47 ` Joonsoo Kim
2017-10-26 7:41 ` Michal Hocko
2017-10-20 7:22 ` Xishi Qiu
2017-10-20 8:17 ` Michal Hocko
2017-10-23 5:26 ` Joonsoo Kim
2017-10-26 13:04 ` Vlastimil Babka
2017-10-26 13:59 ` Michal Hocko
2017-09-18 7:08 ` [PATCH 2/2] mm, memory_hotplug: remove timeout from __offline_memory Michal Hocko
[not found] <AM3PR04MB14892A9D6D2FBCE21B8C1F0FF12B0@AM3PR04MB1489.eurprd04.prod.outlook.com>
2017-11-13 7:33 ` [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Ran Wang
2017-11-13 11:02 ` Michal Hocko
2017-11-14 6:10 ` Ran Wang
2017-11-14 7:06 ` Michal Hocko
2017-11-14 7:45 ` Ran Wang
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