linux-kernel - Re: [this_cpu_xx V6 1/7] this_cpu

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Message-ID: <alpine.DEB.1.10.0910081212200.21951@gentwo.org>
Date:	Thu, 8 Oct 2009 12:15:18 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Tejun Heo <tj@...nel.org>
cc:	linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Subject: Re: [this_cpu_xx V6 1/7] this_cpu_ops: page allocator conversion

On Thu, 8 Oct 2009, Tejun Heo wrote:

> > +static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch);
> > +static DEFINE_PER_CPU(struct per_cpu_pageset, boot_pageset);
>
> This looks much better but I'm not sure whether it's safe.  percpu
> offsets have not been set up before setup_per_cpu_areas() is complete
> on most archs but if all that's necessary is getting the page
> allocator up and running as soon as static per cpu areas and offsets
> are set up (which basically means as soon as cpu init is complete on
> ia64 and setup_per_cpu_areas() is complete on all other archs).  This
> should be correct.  Is this what you're expecting?

paging_init() is called after the per cpu areas have been initialized. So
I thought this would be safe. Tested it on x86.

zone_pcp_init() only sets up the per cpu pointers to the pagesets. That
works regardless of the boot stage. Then then build_all_zonelists()
initializes the actual contents of the per cpu variables.

Finally the per cpu pagesets are allocated from the percpu allocator when
all allocators are up and the pagesets are sized.


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