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SubjectRe: [slub p2 0/4] SLUB: [RFC] Per cpu partial lists V2
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On Mon, 2011-06-20 at 10:32 -0500, Christoph Lameter wrote:
> The following patchset applied on top of the lockless patchset V7. It
> introduces per cpu partial lists which allow a performance increase of
> around ~15 during contention for the nodelock (can be tested using
> hackbench).
>
> These lists help to avoid per nodelocking overhead. Allocator latency
> could be further reduced by making these operations work without
> disabling interrupts (like the fastpath and the free slowpath) as well as
> implementing better ways of handling ther cpu array with partial pages.
>
> I am still not satisfied with the cleanliness of the code after these
> changes. Some review with suggestions as to how to restructure the
> code given these changes in operations would be appreciated.
>
> It is interesting to note that BSD has gone to a scheme with partial
> pages only per cpu (source: Adrian). Transfer of cpu ownerships is
> done using IPIs. Probably too much overhead for our taste. The use
> of a few per cpu partial pages looks to be beneficial though.
>
> Note that there is no performance gain when there is no contention.
>
> Performance:
>
> Before After
> ./hackbench 100 process 200000
> Time: 2299.072 1742.454
> ./hackbench 100 process 20000
> Time: 224.654 182.393
> ./hackbench 100 process 20000
> Time: 227.126 182.780
> ./hackbench 100 process 20000
> Time: 219.608 182.899
> ./hackbench 10 process 20000
> Time: 21.769 18.756
> ./hackbench 10 process 20000
> Time: 21.657 18.938
> ./hackbench 10 process 20000
> Time: 23.193 19.537
> ./hackbench 1 process 20000
> Time: 2.337 2.263
> ./hackbench 1 process 20000
> Time: 2.223 2.271
> ./hackbench 1 process 20000
> Time: 2.269 2.301

Impressive numbers! David, comments on the series?

Pekka



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