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

Konstantin Khlebnikov
2011-07-20T13:28:22Z

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.

nf_conntrack creates separate slab-cache for each net-namespace,
this patch of course not eliminates the chance of failure, but makes it more acceptable.

struct kmem_size for slub is more compact, it uses pecpu-pointers instead of dumb NR_CPUS-size array.
probably better to fix this side...

>
> Pekka