linux-kernel - Re: [PATCH -mm] memcg: fix handling of shmem migration(v2)

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Date:	Wed, 17 Sep 2008 18:18:45 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org, balbir@...ux.vnet.ibm.com,
	xemul@...nvz.org
Subject: Re: [PATCH -mm] memcg: fix handling of shmem migration(v2)

On Wed, 17 Sep 2008 16:55:44 +0900
Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:

> Before this patch, if migrating shmem/tmpfs pages, newpage would be
> charged with PAGE_CGROUP_FLAG_FILE set, while oldpage has been charged
> without the flag.
> 
> The problem here is mem_cgroup_move_lists doesn't clear(or set)
> the PAGE_CGROUP_FLAG_FILE flag, so pc->flags of the newpage
> remains PAGE_CGROUP_FLAG_FILE set even when the pc is moved to
> another lru(anon) by mem_cgroup_move_lists. And this leads to
> incorrect MEM_CGROUP_ZSTAT.
> (In my test, I see an underflow of MEM_CGROUP_ZSTAT(active_file).
> As a result, mem_cgroup_calc_reclaim returns very huge number and
> causes soft lockup on page reclaim.)
> 
> I'm not sure if mem_cgroup_move_lists should handle PAGE_CGROUP_FLAG_FILE
> or not(I suppose it should be used to move between active <-> inactive,
> not anon <-> file), I added MEM_CGROUP_CHARGE_TYPE_SHMEM for precharge
> at shmem's page migration.
> 
> 
> ChangeLog: v1->v2
> - instead of modifying migrate.c, modify memcontrol.c only.
> - add MEM_CGROUP_CHARGE_TYPE_SHMEM.
> 
I'll fix mem_cgroup_charge_cache_page() to use TYPE_SHMEM later.
Thank you.

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>


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