linux-kernel - Re: [PATCH -mmotm 0/5] memcg: per cgroup dirty limit (v6)

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Message-Id: <20100311101726.f58d24e9.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 11 Mar 2010 10:17:26 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Andrea Righi <arighi@...eler.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Vivek Goyal <vgoyal@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Trond Myklebust <trond.myklebust@....uio.no>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Greg Thelen <gthelen@...gle.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Andrew Morton <akpm@...ux-foundation.org>,
	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH -mmotm 0/5] memcg: per cgroup dirty limit (v6)

On Thu, 11 Mar 2010 09:39:13 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> > The performance overhead is not so huge in both solutions, but the impact on
> > performance is even more reduced using a complicated solution...
> > 
> > Maybe we can go ahead with the simplest implementation for now and start to
> > think to an alternative implementation of the page_cgroup locking and
> > charge/uncharge of pages.
> > 
> 
> maybe. But in this 2 years, one of our biggest concerns was the performance.
> So, we do something complex in memcg. But complex-locking is , yes, complex.
> Hmm..I don't want to bet we can fix locking scheme without something complex.
> 
But overall patch set seems good (to me.) And dirty_ratio and dirty_background_ratio
will give us much benefit (of performance) than we lose by small overheads.

IIUC, this series affects trgger for background-write-out.

Could you show some score which dirty_ratio give us benefit in the cases of

	- copying a file in a memcg which hits limit
	  ex) copying a 100M file in 120MB limit.  etc..

	- kernel make performance in limited memcg.
	  ex) making a kernel in 100MB limit (too large ?)
    etc....(when an application does many write and hits memcg's limit.)

But, please get enough ack for changes in generic codes of dirty_ratio.

Thank you for your work.

Regards,
-Kame

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