From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 78F026B0023 for ; Fri, 13 May 2011 01:10:36 -0400 (EDT) Received: from kpbe13.cbf.corp.google.com (kpbe13.cbf.corp.google.com [172.25.105.77]) by smtp-out.google.com with ESMTP id p4D5AWmj027500 for ; Thu, 12 May 2011 22:10:34 -0700 Received: from qwf7 (qwf7.prod.google.com [10.241.194.71]) by kpbe13.cbf.corp.google.com with ESMTP id p4D5AUtx016290 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for ; Thu, 12 May 2011 22:10:31 -0700 Received: by qwf7 with SMTP id 7so1469305qwf.24 for ; Thu, 12 May 2011 22:10:30 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20110513120318.63ff7d0e.kamezawa.hiroyu@jp.fujitsu.com> References: <20110510190216.f4eefef7.kamezawa.hiroyu@jp.fujitsu.com> <20110511182844.d128c995.akpm@linux-foundation.org> <20110512103503.717f4a96.kamezawa.hiroyu@jp.fujitsu.com> <20110511205110.354fa05e.akpm@linux-foundation.org> <20110512132237.813a7c7f.kamezawa.hiroyu@jp.fujitsu.com> <20110512171725.d367980f.kamezawa.hiroyu@jp.fujitsu.com> <20110513120318.63ff7d0e.kamezawa.hiroyu@jp.fujitsu.com> Date: Thu, 12 May 2011 22:10:30 -0700 Message-ID: Subject: Re: [RFC][PATCH 0/7] memcg async reclaim From: Ying Han Content-Type: multipart/alternative; boundary=000e0ce008bc193a0304a3215355 Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki Cc: Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Johannes Weiner , Michal Hocko , "balbir@linux.vnet.ibm.com" , "nishimura@mxp.nes.nec.co.jp" , Greg Thelen --000e0ce008bc193a0304a3215355 Content-Type: text/plain; charset=ISO-8859-1 On Thu, May 12, 2011 at 8:03 PM, KAMEZAWA Hiroyuki < kamezawa.hiroyu@jp.fujitsu.com> wrote: > On Thu, 12 May 2011 17:17:25 +0900 > KAMEZAWA Hiroyuki wrote: > > > On Thu, 12 May 2011 13:22:37 +0900 > > KAMEZAWA Hiroyuki wrote: > > I'll check what codes in vmscan.c or /mm affects memcg and post a > > required fix in step by step. I think I found some.. > > > > After some tests, I doubt that 'automatic' one is unnecessary until > memcg's dirty_ratio is supported. And as Andrew pointed out, > total cpu consumption is unchanged and I don't have workloads which > shows me meaningful speed up. > The total cpu consumption is one way to measure the background reclaim, another thing I would like to measure is a histogram of page fault latency for a heavy page allocation application. I would expect with background reclaim, we will get less variation on the page fault latency than w/o it. Sorry i haven't got chance to run some tests to back it up. I will try to get some data. > But I guess...with dirty_ratio, amount of dirty pages in memcg is > limited and background reclaim can work enough without noise of > write_page() while applications are throttled by dirty_ratio. > Definitely. I have run into the issue while debugging the soft_limit reclaim. The background reclaim became very inefficient if we have dirty pages greater than the soft_limit. Talking w/ Greg about it regarding his per-memcg dirty page limit effort, we should consider setting the dirty ratio which not allowing the dirty pages greater the reclaim watermarks (here is the soft_limit). --Ying > Hmm, I'll study for a while but it seems better to start active soft limit, > (or some threshold users can set) first. > > Anyway, this work makes me to see vmscan.c carefully and I think I can > post some patches for fix, tunes. > > Thanks, > -Kame > > --000e0ce008bc193a0304a3215355 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

On Thu, May 12, 2011 at 8:03 PM, KAMEZAW= A Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
On Thu, 12 May 2011 17:17:25 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> On Thu, 12 May 2011 13:22:37 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> I'll check what codes in vmscan.c or /mm a= ffects memcg and post a
> required fix in step by step. I think I found some..
>

After some tests, I doubt that 'automatic' one is unnecessary= until
memcg's dirty_ratio is supported. And as Andrew pointed out,
total cpu consumption is unchanged and I don't have workloads which
shows me meaningful speed up.

The total= cpu consumption is one way to measure the background reclaim, another thin= g I would like to measure is a histogram of page fault latency
for a heavy page allocation application. I would expect with background rec= laim, we will get less variation on the page fault latency than w/o it.=A0<= /div>

Sorry i haven't got chance to run some tests t= o back it up. I will try to get some data.
=A0
But I guess...with dirty_ratio, amount of dirty pages in memcg is
limited and background reclaim can work enough without noise of
write_page() while applications are throttled by dirty_ratio.

Definitely. I have run into the issue while debuggin= g the soft_limit reclaim. The background reclaim became very inefficient if= we have dirty pages greater than the soft_limit. Talking w/ Greg about it = regarding his per-memcg dirty page limit effort, we should consider setting= the dirty ratio which not allowing the dirty pages greater the reclaim wat= ermarks (here is the soft_limit).

--Ying
=A0
Hmm, I'll study for a while but it seems better to start active soft li= mit,
(or some threshold users can set) first.

Anyway, this work makes me to see vmscan.c carefully and I think I can
post some patches for fix, tunes.

Thanks,
-Kame


--000e0ce008bc193a0304a3215355-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org