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Date: Fri, 24 Jun 2011 20:46:29 +0900
Message-ID: <BANLkTin7TbK1dNjPG6jz_FaJy-QgOjDJaA@mail.gmail.com>
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
From: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
To: Michal Hocko <mhocko@suse.cz>
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>
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2011/6/24 Michal Hocko <mhocko@suse.cz>:
> Sorry, forgot to send my
> Reviewed-by: Michal Hocko <mhocko@suse>
>

Thanks.

> I still have concerns about this way to handle the issue. See the follow
> up discussion in other thread (https://lkml.org/lkml/2011/6/23/135).
>
> Anyway I think that we do not have many other options to handle this.
> Either we unlock, charge, lock&restes or we preallocate, fault in
>
I agree.

> Or am I missing some other ways how to do it? What do others think about
> these approaches?
>

Yes, I'd like to hear other mm specialists' suggestion. and I'll think
other way, again.
Anyway, memory reclaim with holding a lock_page() can cause big latency
or starvation especially when memcg is used. It's better to avoid it.

Thanks,
-Kame
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