Date: Fri, 20 May 2011 16:43:54 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>, Andrew Lutomirski <luto@mit.edu>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        fengguang.wu@intel.com, andi@firstfloor.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, mgorman@suse.de, hannes@cmpxchg.org,
        riel@redhat.com
Subject: Re: Kernel falls apart under light memory pressure (i.e. linking
 vmlinux)
Message-Id: <20110520164354.d43be406.kamezawa.hiroyu@jp.fujitsu.com>
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On Fri, 20 May 2011 14:36:13 +0900
Minchan Kim <minchan.kim@gmail.com> wrote:

> On Fri, May 20, 2011 at 2:08 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > On Fri, 20 May 2011 13:20:15 +0900
> > Minchan Kim <minchan.kim@gmail.com> wrote:
> >
> >> So I want to resolve your problem asap.
> >> We don't have see report about that. Could you do git-bisect?
> >> FYI, Recently, big change of mm is compaction,transparent huge pages.
> >> Kame, could you point out thing related to memcg if you have a mind?
> >>
> >
> > I don't doubt memcg at this stage because it never modify page->flags.
> > Consdering the case, PageActive() is set against off-LRU pages after
> > clear_active_flags() clears it.
> >
> > Hmm, I think I don't understand the lock system fully but...how do you
> > think this ?
> >
> > ==
> >
> > At splitting a hugepage, the routine marks all pmd as "splitting".
> >
> > But assume a racy case where 2 threads run into spit at the
> > same time, one thread wins compound_lock() and do split, another
> > thread should not touch splitted pages.
> 
> Sorry. Now I don't have a time to review in detail.
> When I look it roughly,  page_lock_anon_vma have to prevent it.
> But Andrea needs current this problem and he will catch something we lost. :)
> 
Hmm, maybe I miss something...need to build a test environ on my side.
But I'm not sure I can reproduce it..

Thanks,
-Kame

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