linux-kernel - Re: [PATCH v2 4/6] mm: Only IPI CPUs to drain local pages if they exist

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Message-ID: <4EAAD351.70805@redhat.com>
Date:	Fri, 28 Oct 2011 12:07:45 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Gilad Ben-Yossef <gilad@...yossef.com>
CC:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Russell King <linux@....linux.org.uk>, linux-mm@...ck.org,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	Sasha Levin <levinsasha928@...il.com>
Subject: Re: [PATCH v2 4/6] mm: Only IPI CPUs to drain local pages if they
 exist

On 10/23/2011 11:56 AM, Gilad Ben-Yossef wrote:
> Use a cpumask to track CPUs with per-cpu pages in any zone
> and only send an IPI requesting CPUs to drain these pages
> to the buddy allocator if they actually have pages.

> +/* Which CPUs have per cpu pages  */
> +cpumask_var_t cpus_with_pcp;
> +static DEFINE_PER_CPU(unsigned long, total_cpu_pcp_count);

Does the flushing happen so frequently that it is worth keeping this
state on a per-cpu basis, or would it be better to check each CPU's
pcp info and assemble a cpumask at flush time like done in patch 5?



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