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    SubjectRe: Regression seen for patch "sched:dont decrease idle sleep avg"
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    On Sat, 2006-05-13 at 05:27 -0700, Andrew Morton wrote:
    > (Catching up on lkml)
    >
    > On Thu, 11 May 2006 17:04:11 -0700
    > "Chen, Kenneth W" <kenneth.w.chen@intel.com> wrote:
    >
    > > Tim Chen writes:
    > > > See patch:
    > > > http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=e72ff0bb2c163eb13014ba113701bd42dab382fe
    > >
    > > Con Kolivas wrote on Monday, May 08, 2006 5:43 PM
    > > > This patch corrects a bug in the original code which unintentionally dropped
    > > > the priority of tasks that were idle but were already high priority on other
    > > > merits. It doesn't further increase the priority.
    > >
    > >
    > > This got me to take a non-casual look at that particular git commit. The
    > > first portion of the change log description says perfectly about the intent,
    > > but after studying the code, I have to say that the actual code does not
    > > implement what people say it will do. In recalc_task_prio(), if a task's
    > > sleep_time is more than INTERACTIVE_SLEEP, it will bump up p->sleep_avg all
    > > the way to near maximum (at MAX_SLEEP_AVG - DEF_TIMESLICE), which according
    > > to my calculation, it will have a priority bonus of 4 (out of max 5).
    > >
    > > IOW, for a prolonged sleep, a task will immediately get near maximum priority
    > > boost. Is that what the real intent is? Seems to be on the contrary to what
    > > the source code comments as well.
    > >
    > > I think in the if (sleep_time > INTERACTIVE_SLEEP) block, p->sleep_avg should
    > > be treated similarly like what the "else" block is doing: scale it proportionally
    > > with past sleep time, perhaps not the immediate previously prolonged sleep
    > > because that would for sure bump up priority too fast. A better method might
    > > be p->sleep_avg *= 2 or something like that.
    > >
    >
    > That seems to be a pretty significant discovery. Is anything happening
    > with it?

    When I tried to fix that, I ran into resistance.

    -Mike

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