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Date: Tue, 10 Jan 2012 14:43:21 +0200
Message-ID: <CAOtvUMcJgnGf+RbF6J5zPxi3x4sCt7qoWe+Xd6C8GOhJV=xhqQ@mail.gmail.com>
Subject: Re: [PATCH v6 7/8] mm: only IPI CPUs to drain local pages if they exist
From: Gilad Ben-Yossef <gilad@benyossef.com>
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To: Michal Nazarewicz <mina86@mina86.com>
Cc: Christoph Lameter <cl@linux.com>, linux-kernel@vger.kernel.org, Chris Metcalf <cmetcalf@tilera.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Frederic Weisbecker <fweisbec@gmail.com>, Russell King <linux@arm.linux.org.uk>, linux-mm@kvack.org, Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>, Sasha Levin <levinsasha928@gmail.com>, Rik van Riel <riel@redhat.com>, Andi Kleen <andi@firstfloor.org>, Andrew Morton <akpm@linux-foundation.org>, Alexander Viro <viro@zeniv.linux.org.uk>, linux-fsdevel@vger.kernel.org, Avi Kivity <avi@redhat.com>

2012/1/9 Michal Nazarewicz <mina86@mina86.com>:
> On Mon, 09 Jan 2012 17:35:26 +0100, Christoph Lameter <cl@linux.com> wrot=
e:
>
>> On Sun, 8 Jan 2012, Gilad Ben-Yossef wrote:
>>
>>> @@ -67,6 +67,14 @@ DEFINE_PER_CPU(int, numa_node);
>>> =A0EXPORT_PER_CPU_SYMBOL(numa_node);
>>> =A0#endif
>>>
>>> +/*
>>> + * A global cpumask of CPUs with per-cpu pages that gets
>>> + * recomputed on each drain. We use a global cpumask
>>> + * here to avoid allocation on direct reclaim code path
>>> + * for CONFIG_CPUMASK_OFFSTACK=3Dy
>>> + */
>>> +static cpumask_var_t cpus_with_pcps;
>>
>>
>> Move the static definition into drain_all_pages()?
>
>
> This is initialised in setup_per_cpu_pageset() so it needs to be file
> scoped.

Yes. The cpumask_var_t abstraction is convenient and all but it does
make the allocation
very non obvious when it does not happen in proximity to the variable
use - it doesn't *look* like
a pointer. "syntactic sugar causes cancer of the semicolon" and all that.

Gilad



--=20
Gilad Ben-Yossef
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"Unfortunately, cache misses are an equal opportunity pain provider."
-- Mike Galbraith, LKML

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