linux-kernel - Re: [PATCH] mm: correct page->pfmemalloc to fix deactivate

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Date:	Mon, 13 Aug 2012 13:29:48 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Alex Shi <alex.shi@...el.com>
Cc:	cl@...ux.com, davem@...emloft.net, a.p.zijlstra@...llo.nl,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: correct page->pfmemalloc to fix deactivate_slab
 regression

On Mon, Aug 13, 2012 at 08:14:35PM +0800, Alex Shi wrote:
> commit cfd19c5a9ec (mm: only set page->pfmemalloc when
> ALLOC_NO_WATERMARKS was used) try to narrow down page->pfmemalloc
> setting, but it missed some places the pfmemalloc should be set.
> 
> So, in __slab_alloc, the unalignment pfmemalloc and ALLOC_NO_WATERMARKS
> cause incorrect deactivate_slab() on our core2 server:
> 
>     64.73%           fio  [kernel.kallsyms]     [k] _raw_spin_lock
>                      |
>                      --- _raw_spin_lock
>                         |
>                         |---0.34%-- deactivate_slab
>                         |          __slab_alloc
>                         |          kmem_cache_alloc
>                         |          |
> 
> That causes our fio sync write performance has 40% regression.
> 
> This patch move the checking in get_page_from_freelist, that resolved
> this issue.
> 
> Signed-off-by: Alex Shi <alex.shi@...el.com>

Acked-by: Mel Gorman <mgorman@...e.de>

-- 
Mel Gorman
SUSE Labs
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