linux-kernel - Re: Subject: [RFC MM] mmap_sem scaling: Use mutex and percpu counter instead

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Message-ID: <20091106174439.GB819@basil.fritz.box>
Date:	Fri, 6 Nov 2009 18:44:39 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>, npiggin@...e.de,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Tejun Heo <tj@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"hugh.dickins@...cali.co.uk" <hugh.dickins@...cali.co.uk>
Subject: Re: Subject: [RFC MM] mmap_sem scaling: Use mutex and percpu
	counter instead

On Fri, Nov 06, 2009 at 12:08:54PM -0500, Christoph Lameter wrote:
> On Fri, 6 Nov 2009, Andi Kleen wrote:
> 
> > Yes but all the major calls still take mmap_sem, which is not ranged.
> 
> But exactly that issue is addressed by this patch!

Major calls = mmap, brk, etc.

Only for page faults, not for anything that takes it for write.

Anyways the better reader lock is a step in the right direction, but
I have my doubts it's a good idea to make write really slow here.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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