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    Subject[slub p2 0/4] SLUB: [RFC] Per cpu partial lists V2
    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




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