linux-kernel - Re: [PATCH] SLUB use cmpxchg

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Message-ID: <Pine.LNX.4.64.0708211635320.6062@schroedinger.engr.sgi.com>
Date:	Tue, 21 Aug 2007 16:38:39 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	mingo@...hat.com
Subject: Re: [PATCH] SLUB use cmpxchg_local

On Tue, 21 Aug 2007, Mathieu Desnoyers wrote:

> kmalloc(8)/kfree = 112 cycles
> kmalloc(16)/kfree = 103 cycles
> kmalloc(32)/kfree = 103 cycles
> kmalloc(64)/kfree = 103 cycles
> kmalloc(128)/kfree = 112 cycles
> kmalloc(256)/kfree = 111 cycles
> kmalloc(512)/kfree = 111 cycles
> kmalloc(1024)/kfree = 111 cycles
> kmalloc(2048)/kfree = 121 cycles

Looks good. This improves handling for short lived objects about 
threefold.

> kmalloc(4096)/kfree = 650 cycles
> kmalloc(8192)/kfree = 1042 cycles
> kmalloc(16384)/kfree = 1149 cycles

Hmmm... The page allocator is really bad here....

Could we use the cmpxchg_local approach for the per cpu queues in the 
page_allocator? May have an even greater influence on overall system 
performance than the SLUB changes.

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