linux-kernel - Re: [PATCH 3/7] memcg: add memory.scan

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Message-Id: <20110620130227.6202e8f6.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Mon, 20 Jun 2011 13:02:27 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Ying Han <yinghan@...gle.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>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"bsingharora@...il.com" <bsingharora@...il.com>,
	Michal Hocko <mhocko@...e.cz>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	Andrew Bresticker <abrestic@...gle.com>
Subject: Re: [PATCH 3/7] memcg: add memory.scan_stat

On Mon, 20 Jun 2011 08:41:23 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> On Fri, 17 Jun 2011 15:04:18 -0700
> Ying Han <yinghan@...gle.com> wrote:
> 
> > On Wed, Jun 15, 2011 at 8:53 PM, KAMEZAWA Hiroyuki
> > <kamezawa.hiroyu@...fujitsu.com> wrote:
> > > From e08990dd9ada13cf236bec1ef44b207436434b8e Mon Sep 17 00:00:00 2001
> > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > > Date: Wed, 15 Jun 2011 14:11:01 +0900
> > > Subject: [PATCH 3/7] memcg: add memory.scan_stat
> > >
> > > commit log of commit 0ae5e89 " memcg: count the soft_limit reclaim in..."
> > > says it adds scanning stats to memory.stat file. But it doesn't because
> > > we considered we needed to make a concensus for such new APIs.
> > >
> > > This patch is a trial to add memory.scan_stat. This shows
> > >  - the number of scanned pages
> > >  - the number of recleimed pages
> > >  - the number of elaplsed time (including sleep/pause time)
> > >  for both of direct/soft reclaim and shrinking caused by changing limit
> > >  or force_empty.
> > >
> > > The biggest difference with oringinal Ying's one is that this file
> > > can be reset by some write, as
> > >
> > >  # echo 0 ...../memory.scan_stat
> > >
> > > [kamezawa@...extal ~]$ cat /cgroup/memory/A/memory.scan_stat
> > > scanned_pages_by_limit 358470
> > > freed_pages_by_limit 180795
> > > elapsed_ns_by_limit 21629927
> > > scanned_pages_by_system 0
> > > freed_pages_by_system 0
> > > elapsed_ns_by_system 0
> > > scanned_pages_by_shrink 76646
> > > freed_pages_by_shrink 38355
> > > elappsed_ns_by_shrink 31990670
> > > total_scanned_pages_by_limit 358470
> > > total_freed_pages_by_limit 180795
> > > total_elapsed_ns_by_hierarchical 216299275
> > > total_scanned_pages_by_system 0
> > > total_freed_pages_by_system 0
> > > total_elapsed_ns_by_system 0
> > > total_scanned_pages_by_shrink 76646
> > > total_freed_pages_by_shrink 38355
> > > total_elapsed_ns_by_shrink 31990670
> > >
> > > total_xxxx is for hierarchy management.
> > >
> > > This will be useful for further memcg developments and need to be
> > > developped before we do some complicated rework on LRU/softlimit
> > > management.
> > 
> > Agreed. Actually we are also looking into adding a per-memcg API for
> > adding visibility of
> > page reclaim path. It would be helpful for us to settle w/ the API first.
> > 
> > I am not a fan of names, but how about
> > "/dev/cgroup/memory/memory.reclaim_stat" ?
> > 
> 
> Hm, ok, I have no favorite. 
> 
> 

If I rename, I'll just rename file name as "reclaim_stat" but doesn't
rename internal structures because there is already "struct reclaim_stat".

Hm, to be honest, I don't like the name "reclaim_stat".
(Because in most case, the pages are not freed for reclaim, but for
 hitting limit.)

memory.vmscan_info ?

Thanks,
-Kame

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