linux-kernel - Re: [RFC mm][PATCH 2/5] percpu cached mm counter

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Message-Id: <20091210174230.8367a46c.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 10 Dec 2009 17:42:30 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	cl@...ux-foundation.org,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	minchan.kim@...il.com
Subject: Re: [RFC mm][PATCH 2/5] percpu cached mm counter

On Thu, 10 Dec 2009 09:33:10 +0100
Ingo Molnar <mingo@...e.hu> wrote:

> 
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> 
> > I'm sorry If I miss your point...are you saying remove all mm_counter 
> > completely and remake them under perf ? If so, some proc file 
> > (/proc/<pid>/statm etc) will be corrupted ?
> 
> No, i'm not suggesting that - i'm just suggesting that right now MM 
> stats are not very well suited to be exposed via perf. If we wanted to 
> measure/sample the information in /proc/<pid>/statm it just wouldnt be 
> possible. We have a few events like pagefaults and a few tracepoints as 
> well - but more would be possible IMO.
> 

Ah, ok. More events will be useful.

This patch itself is for reduce(not increase) cache miss in page fault pass..
And counters I'll add is for task monitoring, like ps or top, and for improving
OOM killer. Not for counting events but for showing current _usage_ to users
via procfs or to oom killer.

I'll continue to make an efforts to find better synchronization scheme
rather than adding hook to schedule() but...

Thanks,
-Kame

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