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

From: Konstantin Khlebnikov
Date: Wed Jul 20 2011 - 09:50:33 EST

Pekka Enberg wrote:
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

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,

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.

With NR_CPUS=4096 and MAX_NUMNODES=512 its over 9k!
so it require order-4 page, meanwhile PAGE_ALLOC_COSTLY_ORDER is 3


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