1. 17 Nov, 2005 18 commits
  2. 16 Nov, 2005 21 commits
  3. 15 Nov, 2005 1 commit
    • Chen, Kenneth W's avatar
      [PATCH] ia64: cpu_idle performance bug fix · 1e185b97
      Chen, Kenneth W authored
      Our performance validation on 2.6.15-rc1 caught a disastrous performance
      regression on ia64 with netperf (-98%) and volanomark (-58%) compares to
      previous kernel version 2.6.14-git7.  See the following chart (result
      group 1 & 2).
      
        http://kernel-perf.sourceforge.net/results.machine_id=26.html
      
      We have root caused it to commit 64c7c8f8
      
      This changeset broke the ia64 task resched notification.  In
      sched.c:resched_task(), a reschedule IPI is conditioned upon
      TIF_POLLING_NRFLAG.  However, the above changeset unconditionally set
      the polling thread flag for idle tasks regardless whether pal_halt_light
      is in use or not.  As a result, resched IPI is not sent from
      resched_task().  And since the default behavior on ia64 is to use
      pal_halt_light, we end up delaying the rescheduling task until next
      timer tick, and thus cause the performance regression.
      
      This fixes the performance bug.  I'm glad our performance suite is
      turning up bad performance bug like this in time.
      Signed-off-by: default avatarKen Chen <kenneth.w.chen@intel.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      1e185b97