Re: [PATCH] mm-slab: allocate kmem_cache with __GFP_REPEAT

Mel Gorman
2011-07-20T13:43:53Z

On Wed, Jul 20, 2011 at 04:14:51PM +0300, Pekka Enberg wrote:
> 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@openvz.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.
>

Besides, is allocating from cache_cache really a
PAGE_ALLOC_COSTLY_ORDER allocation? On my laptop at least, it's an
order-2 allocation which is supporting up to 512 CPUs and 512 nodes.

--
Mel Gorman
SUSE Labs