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

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Message-ID: <alpine.DEB.1.10.0911051008260.25718@V090114053VZO-1>
Date:	Thu, 5 Nov 2009 10:10:56 -0500 (EST)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	"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>
Subject: Re: [MM] Make mm counters per cpu instead of atomic

On Thu, 5 Nov 2009, KAMEZAWA Hiroyuki wrote:

> Hmm, I don't fully understand _new_ percpu but...
> In logical (even if not realistic), x86-32 supports up to 512 ? cpus in Kconfig.
> BIGSMP.

x86-32 only supports 32 processors. Plus per cpu areas are only allocated
for the possible processors.

> Then, if 65536 process runs, this consumes
>
> 65536(nr_proc) * 8 (size) * 512(cpus) = 256MBytes.

With 32 possible cpus this results in 16m of per cpu space use.

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