linux-kernel - Re: [MM] Make mm counters per cpu instead of atomic

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Message-ID: <alpine.DEB.2.00.0911240914190.14045@router.home>
Date:	Tue, 24 Nov 2009 09:17:40 -0600 (CST)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"hugh.dickins@...cali.co.uk" <hugh.dickins@...cali.co.uk>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, Tejun Heo <tj@...nel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [MM] Make mm counters per cpu instead of atomic

On Tue, 24 Nov 2009, Zhang, Yanmin wrote:

> > True.... We need to find some alternative to per cpu data to scale mmap
> > sem then.
> I ran lots of benchmarks such like specjbb2005/hackbench/tbench/dbench/iozone
> /sysbench_oltp(mysql)/aim7 against percpu tree(based on 2.6.32-rc7) on a 4*8*2 logical
> cpu machine, and didn't find big result difference between with your patch and without
> your patch.

This affects loads that heavily use mmap_sem. You wont find too many
issues in tests that do not run processes with a large thread count and
cause lots of faults or uses of get_user_pages(). The tests you list are
not of that nature.

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