linux-kernel - Re: [PATCH 3/3] mm: when handling percpu_pagelist_fraction, use on_each

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Message-ID: <5162FFB2.9010201@linux.vnet.ibm.com>
Date:	Mon, 08 Apr 2013 10:34:42 -0700
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Simon Jeons <simon.jeons@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] mm: when handling percpu_pagelist_fraction, use on_each_cpu()
 to set percpu pageset fields.

On 04/06/2013 06:56 PM, Simon Jeons wrote:
> Hi Cody,
> On 04/06/2013 04:33 AM, Cody P Schafer wrote:
>> In free_hot_cold_page(), we rely on pcp->batch remaining stable.
>> Updating it without being on the cpu owning the percpu pageset
>> potentially destroys this stability.
>
> If cpu is off, can its pcp pageset be used in free_hot_code_page()?
>

I don't expect it to be as we use this_cpu_ptr() to access the pcp 
pageset. Unless there is some crazy mode where we can override the cpu a 
task believes it is running on...

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