From: Michal Hocko <mhocko@suse.cz>
To: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Christoph Hellwig <hch@infradead.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>, Rik van Riel <riel@redhat.com>,
Michel Lespinasse <walken@google.com>,
Mel Gorman <mgorman@suse.de>, Lutz Vieweg <lvml@5t9.de>
Subject: Re: [PATCH] mm: preallocate page before lock_page at filemap COW. (WasRe: [PATCH V2] mm: Do not keep page locked during page fault while charging it for memcg
Date: Thu, 23 Jun 2011 15:23:12 +0200 [thread overview]
Message-ID: <20110623132312.GI31593@tiehlicka.suse.cz> (raw)
In-Reply-To: <BANLkTimshUCY5Yq5g9dnY0gi2TRneGscug@mail.gmail.com>
On Thu 23-06-11 22:01:40, Hiroyuki Kamezawa wrote:
> 2011/6/23 Michal Hocko <mhocko@suse.cz>:
> > On Thu 23-06-11 19:01:57, KAMEZAWA Hiroyuki wrote:
> >> On Thu, 23 Jun 2011 11:02:04 +0200
> >> Michal Hocko <mhocko@suse.cz> wrote:
> >>
> >> > On Thu 23-06-11 17:08:11, KAMEZAWA Hiroyuki wrote:
> >> > > On Thu, 23 Jun 2011 09:41:33 +0200
> >> > > Michal Hocko <mhocko@suse.cz> wrote:
> >> > [...]
> >> > > > Other than that:
> >> > > > Reviewed-by: Michal Hocko <mhocko@suse.cz>
> >> > > >
> >> > >
> >> > > I found the page is added to LRU before charging. (In this case,
> >> > > memcg's LRU is ignored.) I'll post a new version with a fix.
> >> >
> >> > Yes, you are right. I have missed that.
> >> > This means that we might race with reclaim which could evict the COWed
> >> > page wich in turn would uncharge that page even though we haven't
> >> > charged it yet.
> >> >
> >> > Can we postpone page_add_new_anon_rmap to the charging path or it would
> >> > just race somewhere else?
> >> >
> >>
> >> I got a different idea. How about this ?
> >> I think this will have benefit for non-memcg users under OOM, too.
> >
> > Could you be more specific? I do not see how preallocation which might
> > turn out to be pointless could help under OOM.
> >
>
> We'll have no page allocation under lock_page() held in this path.
> I think it is good.
But it can also cause that the page, we are about to fault in, is evicted
due to allocation so we would have to do a major fault... This is
probably not that serious, though.
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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next prev parent reply other threads:[~2011-06-23 13:23 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-22 12:06 [PATCH] " Michal Hocko
2011-06-22 12:15 ` Christoph Hellwig
2011-06-22 12:32 ` [PATCH V2] " Michal Hocko
2011-06-23 6:08 ` [PATCH] memcg: unlock page before charging it. (WasRe: " KAMEZAWA Hiroyuki
2011-06-23 7:23 ` Daisuke Nishimura
2011-06-23 7:41 ` Michal Hocko
2011-06-23 8:08 ` KAMEZAWA Hiroyuki
2011-06-23 9:02 ` Michal Hocko
2011-06-23 10:01 ` [PATCH] mm: preallocate page before lock_page at filemap COW. " KAMEZAWA Hiroyuki
2011-06-23 11:58 ` Michal Hocko
2011-06-23 13:01 ` Hiroyuki Kamezawa
2011-06-23 13:23 ` Michal Hocko [this message]
2011-06-23 13:51 ` Hiroyuki Kamezawa
2011-06-24 7:57 ` Michal Hocko
2011-06-24 11:46 ` Hiroyuki Kamezawa
2011-07-12 9:48 ` Michal Hocko
2012-01-26 10:46 ` Lutz Vieweg
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