linux-kernel - Re: [this_cpu_xx V4 13/20] this_cpu

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Date:	Mon, 5 Oct 2009 10:43:12 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>, mingo@...e.hu,
	rusty@...tcorp.com.au, Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [this_cpu_xx V4 13/20] this_cpu_ops: page allocator conversion

On Mon, 5 Oct 2009, Mel Gorman wrote:

> > Right. WE need to move the local_irq_save() up two lines.
>
> Just so I'm 100% clear, IRQ disabling is considered a preemption point?

Yes.

> > Move disable interrupts before the this_cpu_ptr?
> >
>
> In this case, why not move this_cpu_ptr() down until its first use just
> before the if (cold) check? It'll still be within the IRQ disabling but
> without significantly increasing the amount of time the IRQ is disabled.

Good idea. Ill put that into the next release.

> > > > + * Before this call only boot pagesets were available.
> > > > + * Boot pagesets will no longer be used after this call is complete.
> > >
> > > If they are no longer used, do we get the memory back?
> >
> > No we need to keep them for onlining new processors.
> >
>
> That comment would appear to disagree.

The comment is accurate for a processor. Once the pagesets are allocated
for a processor then the boot pageset is no longer used.
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