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

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Message-ID: <20120124084133.GD1660@cmpxchg.org>
Date:	Tue, 24 Jan 2012 09:41:33 +0100
From:	Johannes Weiner <hannes@...xchg.org>
To:	Ying Han <yinghan@...gle.com>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"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>,
	Michal Hocko <mhocko@...e.cz>, Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH] memcg: remove unnecessary thp check at page stat
 accounting

On Mon, Jan 23, 2012 at 12:11:11PM -0800, Ying Han wrote:
> On Wed, Jan 18, 2012 at 11:14 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@...fujitsu.com> 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.
> >
> > 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.
> 
> Sorry, i don't see we changed the "move charge" to "move account" ?

move_account() moves charges.  IMO, it's the function that is a
misnomer and "moving charges" is less ambiguous since we account
several different things in the memory controller.
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