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

Pekka Enberg
2011-07-20T13:42:41Z

On Wed, 20 Jul 2011, Konstantin Khlebnikov wrote:
>> 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.

I'm still surprised you are seeing failures. mm/slab.c hasn't changed
significantly in a long time. Why hasn't anyone reported this before? I'd
still be inclined to shift the blame to the page allocator... Mel,
Christoph?

On Wed, 20 Jul 2011, Konstantin Khlebnikov wrote:
> 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...

So how big is 'struct kmem_cache' for your configuration anyway? Fixing
the per-cpu data structures would be nice but I'm guessing it'll be
slightly painful for mm/slab.c.

Pekka