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    Subject[patch] CFS (Completely Fair Scheduler), v2

    this is the second release of the CFS (Completely Fair Scheduler)
    patchset, against v2.6.21-rc7:

    http://redhat.com/~mingo/cfs-scheduler/sched-cfs-v2.patch

    i'd like to thank everyone for the tremendous amount of feedback and
    testing the v1 patch got - i could hardly keep up with just reading the
    mails! Some of the stuff people addressed i couldnt implement yet, i
    mostly concentrated on bugs, regressions and debuggability.

    there's a fair amount of churn:

    15 files changed, 456 insertions(+), 241 deletions(-)

    But it's an encouraging sign that there was no crash bug found in v1,
    all the bugs were related to scheduling-behavior details. The code was
    tested on 3 architectures so far: i686, x86_64 and ia64. Most of the
    code size increase in -v2 is due to debugging helpers, they'll be
    removed later. (The new /proc/sched_debug file can be used to see the
    fine details of CFS scheduling.)

    Changes since -v1:

    - make nice levels less starvable. (reported by Willy Tarreau)

    - fixed child-runs first. A /proc/sys/kernel/sched_child_runs_first
    flag can be used to turn it on/off. (This might fix the Kaffeine bug
    reported by S.Çağlar Onur <)

    - changed SCHED_FAIR back to SCHED_NORMAL (suggested by Con Kolivas)

    - UP build fix. (reported by Gabriel C)

    - timer tick micro-optimization (Dmitry Adamushko)

    - preemption fix: sched_class->check_preempt_curr method to decide
    whether to preempt after a wakeup (or at a timer tick). (Found via a
    fairness-test-utility written for CFS by Mike Galbraith)

    - start forked children with neutral statistics instead of trying to
    inherit them from the parent: Willy Tarreau reported that this
    results in better behavior on extreme workloads, and it also
    simplifies the code quite nicely. Removed sched_exit() and the
    ->task_exit() methods.

    - make nice levels independent of the sched_granularity value

    - new /proc/sched_debug file listing runqueue details and the rbtree

    - new SCH-* fields in /proc/<NR>/status to see scheduling details

    - new cpu-hog feature (off by default) and sysctl tunable to set it:
    /proc/sys/kernel/sched_max_hog_history_ns tunable defaults to
    0 (off). Positive values are meant the maximum 'memory' that the
    scheduler has of CPU hogs.

    - various code cleanups

    - added more statistics temporarily: sum_exec_runtime,
    sum_wait_runtime.

    - added -CFS-v2 to EXTRAVERSION

    as usual, any sort of feedback, bugreports, fixes and suggestions are
    more than welcome,

    Ingo
    -
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