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SubjectRe: Fw: [PATCH] NUMA Slab Allocator
Martin J. Bligh wrote:

>That'd be my inclination .... but OTOH, we do that for pagecache OK.
>
The page cache doesn't have a global hash table.

> Dunno,
>I'm torn. Depends if there's locality on the file access or not, I guess.
>Is there any *harm* in doing it node local .... perhaps creating a node
>mem pressure imbalance (OTOH, there's loads of stuff that does that anyway ;-))
>
>
>
The harm is slower kmem_cache_free and a lower hit ratio for the per-cpu
caches: kmem_cache_free must identify and return wrong node objects, and
due to these returns, the per-cpu array is more often empty in
kmem_cache_alloc.

IIRC someone from SGI wrote that they have seen bad performance in
fork-bomb tests on large cpu count systems which might be caused by
inter-node traffic on the mm_struct structure and that they think that a
numa aware allocator would help. As far as I know no tests were done to
very that assumption.

--
Manfred
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