From: Shakeel Butt <shakeelb@google.com>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Alex Shi <alex.shi@linux.alibaba.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Matthew Wilcox <willy@infradead.org>, Qian Cai <cai@lca.pw>,
Chris Wilson <chris@chris-wilson.co.uk>,
Kuo-Hsin Yang <vovoy@chromium.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>
Subject: Re: [PATCH 4/5] mm: fix check_move_unevictable_pages() on THP
Date: Mon, 31 Aug 2020 07:44:33 -0700 [thread overview]
Message-ID: <CALvZod793qTH_i82nrcFCuyXVW2YoDDqcRoXrgkEd2E2_7rTrA@mail.gmail.com> (raw)
In-Reply-To: <alpine.LSU.2.11.2008301405000.5954@eggly.anvils>
On Sun, Aug 30, 2020 at 2:08 PM Hugh Dickins <hughd@google.com> wrote:
>
> check_move_unevictable_pages() is used in making unevictable shmem pages
> evictable: by shmem_unlock_mapping(), drm_gem_check_release_pagevec() and
> i915/gem check_release_pagevec(). Those may pass down subpages of a huge
> page, when /sys/kernel/mm/transparent_hugepage/shmem_enabled is "force".
>
> That does not crash or warn at present, but the accounting of vmstats
> unevictable_pgs_scanned and unevictable_pgs_rescued is inconsistent:
> scanned being incremented on each subpage, rescued only on the head
> (since tails already appear evictable once the head has been updated).
>
> 5.8 commit 5d91f31faf8e ("mm: swap: fix vmstats for huge page") has
> established that vm_events in general (and unevictable_pgs_rescued in
> particular) should count every subpage: so follow that precedent here.
>
> Do this in such a way that if mem_cgroup_page_lruvec() is made stricter
> (to check page->mem_cgroup is always set), no problem: skip the tails
> before calling it, and add thp_nr_pages() to vmstats on the head.
>
> Signed-off-by: Hugh Dickins <hughd@google.com>
Thanks for catching this.
Reviewed-by: Shakeel Butt <shakeelb@google.com>
next prev parent reply other threads:[~2020-08-31 14:44 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-30 20:57 [PATCH 0/5] mm: fixes to past from future testing Hugh Dickins
2020-08-30 20:59 ` [PATCH 1/5] ksm: reinstate memcg charge on copied pages Hugh Dickins
2020-08-31 14:40 ` Shakeel Butt
2020-09-01 15:01 ` Johannes Weiner
2020-08-30 21:01 ` [PATCH 2/5] mm: migration of hugetlbfs page skip memcg Hugh Dickins
2020-08-31 14:40 ` Shakeel Butt
2020-09-01 15:02 ` Johannes Weiner
2020-08-30 21:08 ` [PATCH 4/5] mm: fix check_move_unevictable_pages() on THP Hugh Dickins
2020-08-31 14:44 ` Shakeel Butt [this message]
2020-09-01 2:04 ` Alex Shi
2020-09-01 3:59 ` Hugh Dickins
2020-09-01 15:57 ` Yang Shi
2020-08-30 21:09 ` [PATCH 5/5] mlock: fix unevictable_pgs event counts " Hugh Dickins
2020-08-31 14:45 ` Shakeel Butt
2020-09-01 15:41 ` Yang Shi
2020-09-01 2:28 ` [PATCH 0/5] mm: fixes to past from future testing Alex Shi
2020-09-01 4:08 ` Hugh Dickins
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