On 12/11/2013 01:09 PM, Johannes Weiner wrote:
> Dave Hansen noted a regression in a microbenchmark that loops around
> open() and close() on an 8-node NUMA machine and bisected it down to
> 81c0a2bb515f ("mm: page_alloc: fair zone allocator policy"). That
> change forces the slab allocations of the file descriptor to spread
> out to all 8 nodes, causing remote references in the page allocator
> and slab.
>
> The round-robin policy is only there to provide fairness among memory
> allocations that are reclaimed involuntarily based on pressure in each
> zone. It does not make sense to apply it to unreclaimable kernel
> allocations that are freed manually, in this case instantly after the
> allocation, and incur the remote reference costs twice for no reason.
>
> Only round-robin allocations that are usually freed through page
> reclaim or slab shrinking.
>
> Bisected-by: Dave Hansen <dave.han...@intel.com>
> Signed-off-by: Johannes Weiner <han...@cmpxchg.org>
> Cc: <sta...@kernel.org>
Reviewed-by: Rik van Riel <r...@redhat.com>
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