From: Michal Hocko <mhocko@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Zi Yan <zi.yan@sent.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Vlastimil Babka <vbabka@suse.cz>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: shmem: enable thp migration (Re: [PATCH v1] mm: consider non-anonymous thp as unmovable page)
Date: Wed, 11 Apr 2018 21:43:26 +0200 [thread overview]
Message-ID: <20180411194326.GN23400@dhcp22.suse.cz> (raw)
In-Reply-To: <20180411122739.25d1700099222eb647b0c620@linux-foundation.org>
On Wed 11-04-18 12:27:39, Andrew Morton wrote:
> On Wed, 11 Apr 2018 11:26:11 +0200 Michal Hocko <mhocko@kernel.org> wrote:
>
> > On Fri 06-04-18 03:07:11, Naoya Horiguchi wrote:
> > > >From e31ec037701d1cc76b26226e4b66d8c783d40889 Mon Sep 17 00:00:00 2001
> > > From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> > > Date: Fri, 6 Apr 2018 10:58:35 +0900
> > > Subject: [PATCH] mm: enable thp migration for shmem thp
> > >
> > > My testing for the latest kernel supporting thp migration showed an
> > > infinite loop in offlining the memory block that is filled with shmem
> > > thps. We can get out of the loop with a signal, but kernel should
> > > return with failure in this case.
> > >
> > > What happens in the loop is that scan_movable_pages() repeats returning
> > > the same pfn without any progress. That's because page migration always
> > > fails for shmem thps.
> > >
> > > In memory offline code, memory blocks containing unmovable pages should
> > > be prevented from being offline targets by has_unmovable_pages() inside
> > > start_isolate_page_range().
> > >
> > > So it's possible to change migratability
> > > for non-anonymous thps to avoid the issue, but it introduces more complex
> > > and thp-specific handling in migration code, so it might not good.
> > >
> > > So this patch is suggesting to fix the issue by enabling thp migration
> > > for shmem thp. Both of anon/shmem thp are migratable so we don't need
> > > precheck about the type of thps.
> > >
> > > Fixes: commit 72b39cfc4d75 ("mm, memory_hotplug: do not fail offlining too early")
> > > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> > > Cc: stable@vger.kernel.org # v4.15+
> >
> > I do not really feel qualified to give my ack but this is the right
> > approach for the fix. We simply do expect that LRU pages are migrateable
> > as well as zone_movable pages.
> >
> > Andrew, do you plan to take it (with Kirill's ack).
> >
>
> Sure. What happened with "Michal's fix in another email"
> (https://lkml.kernel.org/r/20180406051452.GB23467@hori1.linux.bs1.fc.nec.co.jp)?
I guess you meant http://lkml.kernel.org/r/20180405190405.GS6312@dhcp22.suse.cz
Well, that would be a workaround in case we didn't have a proper fix. It
is much simpler but it wouldn't make backporting to older kernels any
easier because it depends on other non-trivial changes you already have
in your tree. So having a full THP pagecache migration support is
preferred of course.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-04-11 19:43 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-03 4:46 [PATCH v1] mm: consider non-anonymous thp as unmovable page Naoya Horiguchi
2018-04-03 7:59 ` Michal Hocko
2018-04-03 8:24 ` Naoya Horiguchi
2018-04-03 8:34 ` Michal Hocko
2018-04-03 10:54 ` Kirill A. Shutemov
2018-04-03 10:58 ` Michal Hocko
2018-04-03 11:16 ` Kirill A. Shutemov
2018-04-03 11:33 ` Michal Hocko
2018-04-05 8:59 ` Michal Hocko
2018-04-05 12:28 ` Kirill A. Shutemov
2018-04-05 12:48 ` Michal Hocko
2018-04-05 13:40 ` Kirill A. Shutemov
2018-04-05 15:05 ` Michal Hocko
2018-04-05 15:55 ` Kirill A. Shutemov
2018-04-05 16:03 ` Michal Hocko
2018-04-05 17:58 ` Zi Yan
2018-04-05 19:04 ` Michal Hocko
2018-04-05 19:09 ` Zi Yan
2018-04-06 3:07 ` [PATCH] mm: shmem: enable thp migration (Re: [PATCH v1] mm: consider non-anonymous thp as unmovable page) Naoya Horiguchi
2018-04-06 5:14 ` Naoya Horiguchi
2018-04-06 7:08 ` Michal Hocko
2018-04-09 7:14 ` Naoya Horiguchi
2018-04-10 11:16 ` Kirill A. Shutemov
2018-04-11 9:26 ` Michal Hocko
2018-04-11 19:27 ` Andrew Morton
2018-04-11 19:43 ` Michal Hocko [this message]
2018-04-23 3:03 ` Matthew Wilcox
2018-04-23 7:21 ` Naoya Horiguchi
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