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    Subject[patch] CFS scheduler, -v5

    i'm pleased to announce release -v5 of the CFS scheduler patchset. The
    patch against v2.6.21-rc7 and v2.6.20.7 can be downloaded from:

    this CFS release mainly fixes regressions and improves interactivity:

    13 files changed, 211 insertions(+), 199 deletions(-)

    the biggest user-visible change in -v5 are various interactivity
    improvements (especially under higher load) to fix reported regressions,
    and an improved way of handling nice levels. There's also a new
    sys_sched_yield_to() syscall implementation for i686 and x86_64.

    All known regressions have been fixed. (knock on wood)

    [ Note: while CFS's default preemption granularity is currently set to 5
    msecs, this value does not directly transform into timeslices: for
    example two CPU-intense tasks will have effective timeslices of 10
    msecs with this setting. ]

    Changes since -v4:

    - interactivity bugfix: fix xterm latencies and general desktop delays
    and child task startup delays under load. (reported by Willy Tarreau
    and Caglar Onur)

    - bugfix: the in_atomic_preempt_off() call on !PREEMPT_BKL was buggy
    and spammed the console with bogus warnings.

    - implementation fix: make the nice levels implementation
    starvation-free and smpnice-friendly. Remove the nice_offset hack.

    - feature: add initial sys_sched_yield_to() implementation. Not hooked
    into the futex code yet, but testers are encouraged to give the
    syscalls a try, on i686 the new syscall is __NR_yield_to==320, on
    x86_64 it's __NR_yield_to==280. The prototype is
    sys_sched_yield_to(pid_t), as suggested by Ulrich Drepper.

    - usability feature: add CONFIG_RENICE_X: those who dont want the
    kernel to renice X should disable this option. (the boot option and
    the sysctl is still available too)

    - removed my home-made "Con was right about scheduling fairness"
    attribution to Con's scheduler interactivity work - some have
    suggested that Con might want to see another text there. Con,
    please feel free to fill it in!

    - feature: make the CPU usage of nice levels logarithmic instead of
    linear. This is more usable and more intuitive. (Going four nice
    levels forward/backwards give half/twice the CPU power) [ This was
    requested a number of times in the past few years and is
    straightforward under CFS because there nice levels are not tied to
    any timeslice distribution mechanism. ]

    - cleanup: removed the stupid "Ingo was here" banner printk from
    sched_init(), the -cfs EXTRAVERSION serves the purpose (of
    identifying a booted up kernel as a CFS one) equally well.

    - various other code cleanups

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

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      Last update: 2007-04-23 03:17    [W:0.024 / U:22.512 seconds]
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