releases/2.6.24.1/sched-let-nice-tasks-have-smaller-impact.patch

   1 From ef9884e6f29bbe1075204f962a00f7533bf7e8f3 Mon Sep 17 00:00:00 2001
   2 From: Peter Zijlstra <a.p.zijlstra@chello.nl>
   3 Date: Thu, 31 Jan 2008 22:45:22 +0100
   4 Subject: sched: let +nice tasks have smaller impact
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=utf-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 From: Peter Zijlstra <a.p.zijlstra@chello.nl>
  10
  11 patch ef9884e6f29bbe1075204f962a00f7533bf7e8f3 in mainline.
  12
  13 Michel Dänzr has bisected an interactivity problem with
  14 plus-reniced tasks back to this commit:
  15
  16  810e95ccd58d91369191aa4ecc9e6d4a10d8d0c8 is first bad commit
  17  commit 810e95ccd58d91369191aa4ecc9e6d4a10d8d0c8
  18  Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
  19  Date:   Mon Oct 15 17:00:14 2007 +0200
  20
  21  sched: another wakeup_granularity fix
  22
  23       unit mis-match: wakeup_gran was used against a vruntime
  24
  25 fix this by assymetrically scaling the vtime of positive reniced
  26 tasks.
  27
  28 Bisected-by: Michel Dänzer <michel@tungstengraphics.com>
  29 Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
  30 Signed-off-by: Ingo Molnar <mingo@elte.hu>
  31 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  32
  33 ---
  34  kernel/sched_fair.c |    6 +++++-
  35  1 file changed, 5 insertions(+), 1 deletion(-)
  36
  37 --- a/kernel/sched_fair.c
  38 +++ b/kernel/sched_fair.c
  39 @@ -867,7 +867,11 @@ static void check_preempt_wakeup(struct
  40         }
  41
  42         gran = sysctl_sched_wakeup_granularity;
  43 -       if (unlikely(se->load.weight != NICE_0_LOAD))
  44 +       /*
  45 +        * More easily preempt - nice tasks, while not making
  46 +        * it harder for + nice tasks.
  47 +        */
  48 +       if (unlikely(se->load.weight > NICE_0_LOAD))
  49                 gran = calc_delta_fair(gran, &se->load);
  50
  51         if (pse->vruntime + gran < se->vruntime)