linux-kernel - Re: [PATCH 3/3] percpu: use percpu allocator on UP too

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Message-ID: <4C81ED2C.6000304@cs.helsinki.fi>
Date:	Sat, 04 Sep 2010 09:54:36 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Tejun Heo <tj@...nel.org>
CC:	Christoph Lameter <cl@...ux.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] percpu: use percpu allocator on UP too

On 3.9.2010 19.26, Tejun Heo wrote:
> On UP, percpu allocations were redirected to kmalloc.  This has the
> following problems.
>
> * For certain amount of allocations (determined by
>    PERCPU_DYNAMIC_EARLY_SLOTS and PERCPU_DYNAMIC_EARLY_SIZE), percpu
>    allocator can be used before the usual kernel memory allocator is
>    brought online.  On SMP, this is used to initialize the kernel
>    memory allocator.
>
> * percpu allocator honors alignment upto PAGE_SIZE but kmalloc()
>    doesn't.  For example, workqueue makes use of larger alignments for
>    cpu_workqueues.
>
> Currently, users of percpu allocators need to handle UP differently,
> which is somewhat fragile and ugly.  Other than small amount of
> memory, there isn't much to lose by enabling percpu allocator on UP.
> It can simply use kernel memory based chunk allocation which was added
> for SMP archs w/o MMUs.
>
> This patch removes mm/percpu_up.c, builds mm/percpu.c on UP too and
> makes UP build use percpu-km.  As percpu addresses and kernel
> addresses are always identity mapped and static percpu variables don't
> need any special treatment, nothing is arch dependent and mm/percpu.c
> implements generic setup_per_cpu_areas() for UP.
>
> Signed-off-by: Tejun Heo<tj@...nel.org>
> Cc: Christoph Lameter<cl@...ux-foundation.org>
> Cc: Pekka Enberg<penberg@...helsinki.fi>

Acked-by: Pekka Enberg <penberg@...nel.org>

Is this going into some public append-only branch I could cherry-pick 
the changeset from to my 'slub/cleanups' branch?

			Pekka
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