Re: [PATCH 3/6] memcg: remove PCG_MOVE_LOCK flag from page_cgroup

[Johannes Weiner]

On Fri, Feb 17, 2012 at 06:26:51PM +0900, KAMEZAWA Hiroyuki wrote:
> >From 62a96c625be0c30fc5828d88685b6873ed254060 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> 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()
> 
> Acked-by: Greg Thelen <gthelen@xxxxxxxxxx>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
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