linux-kernel - Re: linux-next: build failure after merge of the final tree (slab tree related)

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Message-ID: <alpine.DEB.2.00.1008252014560.10986@chino.kir.corp.google.com>
Date:	Wed, 25 Aug 2010 20:16:05 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Christoph Lameter <cl@...ux.com>
cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>
Subject: Re: linux-next: build failure after merge of the final tree (slab
 tree related)

On Wed, 25 Aug 2010, Christoph Lameter wrote:

> > > +	 * Special hack for UP mode. allocpercpu() falls back to kmalloc
> > > +	 * operations. So we cannot use that before the slab allocator is up
> > > +	 * Simply get the smallest possible compound page. The page will be
> > > +	 * released via kfree() when the cpu caches are resized later.
> > > +	 */
> > > +	if (slab_state < UP)
> > > +		s->cpu_slab = (__percpu void *)__get_free_page(GFP_NOWAIT, 1);
> >
> > __get_free_pages() takes an order argument.
> 
> Right. Patch not refreshed after the last tinzy winzy change. Seems that I
> got a bit rusty.
> 
> Subject: Slub: UP bandaid
> 
> Since the percpu allocator does not provide early allocation in UP
> mode (only in SMP configurations) use __get_free_page() to improvise
> a compound page allocation that can be later freed via kfree().
> 
> Compound pages will be released when the cpu caches are resized.
> 
> Signed-off-by: Christoph Lameter <cl@...ux.com>

Acked-by: David Rientjes <rientjes@...gle.com>

I'm really hoping that we can remove this hack soon when the percpu 
allocator can handle these allocations on UP without any specialized slab 
behavior.
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