linux-kernel - Re: + page_alloc-oops-when-setting-percpu_pagelist

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Date:	Wed, 17 Jun 2009 13:34:26 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Dimitri Sivanich <sivanich@....com>
cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, mel@....ul.ie,
	nickpiggin@...oo.com.au, linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, akpm@...ux-foundation.org
Subject: Re: + page_alloc-oops-when-setting-percpu_pagelist_fraction.patch
 added to -mm tree

On Wed, 17 Jun 2009, Dimitri Sivanich wrote:

> > pcp is only protected local_irq_save(), not spin lock. it assume
> > each cpu have different own pcp. but this patch break this assumption.
> > Now, we can share boot_pageset by multiple cpus.
> >
>
> I'm not quite understanding what you mean.
>
> Prior to the cpu going down, each unpopulated zone pointed to the boot_pageset (per_cpu_pageset) for it's cpu (it's array element), so things had been set up this way already.  I could be missing something, but am not sure why restoring this would be a risk?

The boot_pageset is supposed to be per cpu and this patch preserves it.

However, all zones for a cpu have just a single boot pageset. Maybe that
was what threw off Kosaki?

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