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    Subject[patch] CFS scheduler, -v19

    i'm pleased to announce release -v19 of the CFS scheduler patchset.

    The rolled-up CFS patch against today's -git kernel, v2.6.22-rc7,
    v2.6.22-rc6-mm1, v2.6.21.5 or v2.6.20.14 can be downloaded from the
    usual place:

    http://people.redhat.com/mingo/cfs-scheduler/

    The biggest user-visible change in -v19 is reworked sleeper fairness:
    it's similar in behavior to -v18 but works more consistently across nice
    levels. Fork-happy workloads (like kernel builds) should behave better
    as well. There are also a handful of speedups: unsigned math, 32-bit
    speedups, O(1) task pickup, debloating and other micro-optimizations.

    Changes since -v18:

    - merged the group-scheduling CFS-core changes from Srivatsa Vaddagiri.
    This makes up for the bulk of the changes in -v19 but has no
    behavioral impact. The final group-fairness enabler patch is now a
    small and lean add-on patch to CFS.

    - fix the bloat noticed by Andrew. On 32-bit it's now this:

    text data bss dec hex filename
    24362 3905 24 28291 6e83 sched.o-rc7
    33015 2538 20 35573 8af5 sched.o-v18
    25805 2426 20 28251 6e5b sched.o-v19

    so it's a net win compared to vanilla. On 64-bit it's even better:

    text data bss dec hex filename
    35732 40314 2168 78214 13186 sched.o.x64-rc7
    41397 37642 2168 81207 13d37 sched.o.x64-v18
    36132 37410 2168 75710 127be sched.o.x64-v19

    ( and there's also a +1.5K data win per CPU on x32, which is not
    shown here. [+3.0K data win per CPU on x64.] )

    - good number of core code updates, cleanups and streamlining.
    (Mike Galbraith, Srivatsa Vaddagiri, Dmitry Adamushko, me.)

    - use unsigned data types almost everywhere in CFS. This produces
    faster and smaller code, and simplifies the logic.

    - turn as many 'u64' data types into 'unsigned long' as possible, to
    reduce the 32-bit footprint and to reduce 64-bit arithmetics.

    - replaced the nr_running based 'sleep fairness' logic with a more
    robust concept. The end-result is similar in behavior to v18, but
    negative nice levels are handled much better in this scheme.

    - speedup: O(1) task pickup by Srivatsa Vaddagiri. [sleep/wakeup is
    O(log2(nr_running)).] This gives 5-10% better hackbench 100/500
    results on a 4-way box.

    - fix: set idle->sched_class back to &idle_sched_class in
    migration_call(). (Dmitry Adamushko)

    - cleanup: use an enum for the sched_feature flags. (suggested by
    Andrew Morton)

    - cleanup: turn the priority macros into inlines. (suggested by
    Andrew Morton)

    - (other cleanups suggested by Andrew Morton)

    - debug: split out the debugging data into CONFIG_SCHED_DEBUG.

    As usual, any sort of feedback, bugreport, fix and suggestion is more
    than welcome!

    Ingo
    -
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