linux-kernel - Re: [PATCH 5/7] memcg: add per cgroup dirty pages accounting

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Date:	Sun, 8 Jul 2012 22:45:38 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Sha Zhengju <handai.szj@...il.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, gthelen@...gle.com, yinghan@...gle.com,
	akpm@...ux-foundation.org, mhocko@...e.cz,
	linux-kernel@...r.kernel.org, Sha Zhengju <handai.szj@...bao.com>
Subject: Re: [PATCH 5/7] memcg: add per cgroup dirty pages accounting

On Tue, Jul 03, 2012 at 02:57:08PM +0900, KAMEZAWA Hiroyuki wrote:
> (2012/06/28 20:04), Sha Zhengju wrote:
> > From: Sha Zhengju <handai.szj@...bao.com>
> > 
> > This patch adds memcg routines to count dirty pages, which allows memory controller
> > to maintain an accurate view of the amount of its dirty memory and can provide some
> > info for users while group's direct reclaim is working.
> > 
> > After Kame's commit 89c06bd5(memcg: use new logic for page stat accounting), we can
> > use 'struct page' flag to test page state instead of per page_cgroup flag. But memcg
> > has a feature to move a page from a cgroup to another one and may have race between
> > "move" and "page stat accounting". So in order to avoid the race we have designed a
> > bigger lock:
> > 
> >           mem_cgroup_begin_update_page_stat()
> >           modify page information	-->(a)
> >           mem_cgroup_update_page_stat()  -->(b)
> >           mem_cgroup_end_update_page_stat()
> > 
> > It requires (a) and (b)(dirty pages accounting) can stay close enough.
> > 
> > In the previous two prepare patches, we have reworked the vfs set page dirty routines
> > and now the interfaces are more explicit:
> > 	incrementing (2):
> > 		__set_page_dirty
> > 		__set_page_dirty_nobuffers
> > 	decrementing (2):
> > 		clear_page_dirty_for_io
> > 		cancel_dirty_page
> > 
> > 
> > Signed-off-by: Sha Zhengju <handai.szj@...bao.com>
> 
> Thank you. This seems much cleaner than expected ! very good.
> 
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujtisu.com>

I have the same good feelings :)

Acked-by: Fengguang Wu <fengguang.wu@...el.com>

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