linux-kernel - Re: [PATCH] mm-slab: allocate kmem_cache with __GFP

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Date:	Wed, 20 Jul 2011 16:14:51 +0300 (EEST)
From:	Pekka Enberg <penberg@...nel.org>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Matt Mackall <mpm@...enic.com>,
	mgorman@...e.de
Subject: Re: [PATCH] mm-slab: allocate kmem_cache with __GFP_REPEAT

On Wed, 20 Jul 2011, Konstantin Khlebnikov wrote:
> Order of sizeof(struct kmem_cache) can be bigger than PAGE_ALLOC_COSTLY_ORDER,
> thus there is a good chance of unsuccessful allocation.
> With __GFP_REPEAT buddy-allocator will reclaim/compact memory more aggressively.
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
> ---
> mm/slab.c |    2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index d96e223..53bddc8 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -2304,7 +2304,7 @@ kmem_cache_create (const char *name, size_t size, size_t align,
> 		gfp = GFP_NOWAIT;
>
> 	/* Get cache's description obj. */
> -	cachep = kmem_cache_zalloc(&cache_cache, gfp);
> +	cachep = kmem_cache_zalloc(&cache_cache, gfp | __GFP_REPEAT);
> 	if (!cachep)
> 		goto oops;

The changelog isn't that convincing, really. This is kmem_cache_create() 
so I'm surprised we'd ever get NULL here in practice. Does this fix some 
problem you're seeing? If this is really an issue, I'd blame the page 
allocator as GFP_KERNEL should just work.

 			Pekka
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