From: Michal Hocko <mhocko@suse.cz>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [patch] mm: memcontrol: clarify migration where old page is uncharged
Date: Mon, 20 Oct 2014 21:45:05 +0200 [thread overview]
Message-ID: <20141020194505.GE505@dhcp22.suse.cz> (raw)
In-Reply-To: <1413732647-16043-1-git-send-email-hannes@cmpxchg.org>
On Sun 19-10-14 11:30:47, Johannes Weiner wrote:
> Better explain re-entrant migration when compaction races with
> reclaim, and also mention swapcache readahead pages as possible
> uncharged migration sources.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
> ---
> mm/memcontrol.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index fc1d7ca96b9d..76892eb89d26 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -6166,7 +6166,12 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
> if (PageCgroupUsed(pc))
> return;
>
> - /* Re-entrant migration: old page already uncharged? */
> + /*
> + * Swapcache readahead pages can get migrated before being
> + * charged, and migration from compaction can happen to an
> + * uncharged page when the PFN walker finds a page that
> + * reclaim just put back on the LRU but has not released yet.
> + */
> pc = lookup_page_cgroup(oldpage);
> if (!PageCgroupUsed(pc))
> return;
> --
> 2.1.2
>
--
Michal Hocko
SUSE Labs
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prev parent reply other threads:[~2014-10-20 19:45 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-19 15:30 [patch] mm: memcontrol: clarify migration where old page is uncharged Johannes Weiner
2014-10-20 19:45 ` Michal Hocko [this message]
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