linux-kernel - Re: [PATCH] memcg: remove unnecessary thp check at page stat accounting

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Message-Id: <20120120092928.d6514341.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 20 Jan 2012 09:29:28 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>, Ying Han <yinghan@...gle.com>
Subject: Re: [PATCH] memcg: remove unnecessary thp check at page stat
 accounting

On Thu, 19 Jan 2012 10:34:10 +0100
Michal Hocko <mhocko@...e.cz> wrote:

> On Thu 19-01-12 16:14:45, KAMEZAWA Hiroyuki wrote:
> > Thank you very much for reviewing previous RFC series.
> > This is a patch against memcg-devel and linux-next (can by applied without HUNKs).
> > 
> > ==
> > 
> > From 64641b360839b029bb353fbd95f7554cc806ed05 Mon Sep 17 00:00:00 2001
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > Date: Thu, 12 Jan 2012 16:08:33 +0900
> > Subject: [PATCH] memcg: remove unnecessary thp check in mem_cgroup_update_page_stat()
> > 
> > commit 58b318ecf(memcg-devel)
> >     memcg: make mem_cgroup_split_huge_fixup() more efficient
> > removes move_lock_page_cgroup() in thp-split path.
> 
> I wouldn't refer to something which will change its commit id by its
> SHA. I guess the subject is sufficient. 

> Btw. do we really need to
> mention this? Is it just to make sure that this doesn't get merged
> withtout the mentioned patch?
> 

Hmm, ok. Yes, just informing this patch depends on that patch.




> > So, We do not have to check PageTransHuge in mem_cgroup_update_page_stat
> > and fallback into the locked accounting because both move charge and thp
> > split up are done with compound_lock so they cannot race. update vs.
> > move is protected by the mem_cgroup_stealed sufficiently.
> > 
> > PageTransHuge pages shouldn't appear in this code path currently because
> > we are tracking only file pages at the moment but later we are planning
> > to track also other pages (e.g. mlocked ones).
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
> Other than that
> Acked-by: Michal Hocko <mhocko@...e.cz>
> 
Thank you.

-Kame

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