linux-kernel - Re: [PATCH 3/6 v4] memcg: remove PCG_MOVE_LOCK flag from page

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Date:	Mon, 13 Feb 2012 23:21:45 -0800
From:	Greg Thelen <gthelen@...gle.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	Ying Han <yinghan@...gle.com>, Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 3/6 v4] memcg: remove PCG_MOVE_LOCK flag from page_cgroup.

On Mon, Feb 13, 2012 at 7:13 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
> From ffd1b013fe294a80c12e3f30e85386135a6fb284 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Date: Thu, 2 Feb 2012 11:49:59 +0900
> Subject: [PATCH 3/6] memcg: remove PCG_MOVE_LOCK flag from page_cgroup.
>
> PCG_MOVE_LOCK is used for bit spinlock to avoid race between overwriting
> pc->mem_cgroup and page statistics accounting per memcg.
> This lock helps to avoid the race but the race is very rare because moving
> tasks between cgroup is not a usual job.
> So, it seems using 1bit per page is too costly.
>
> This patch changes this lock as per-memcg spinlock and removes PCG_MOVE_LOCK.
>
> If smaller lock is required, we'll be able to add some hashes but
> I'd like to start from this.
>
> Changelog:
>  - fixed to pass memcg as an argument rather than page_cgroup.
>    and renamed from move_lock_page_cgroup() to move_lock_mem_cgroup()
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

Seems good.  Thanks.

Acked-by: Greg Thelen <gthelen@...gle.com>
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