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  1. 08 Oct, 2009 1 commit
    • Arjan van de Ven's avatar
      x86, timers: Check for pending timers after (device) interrupts · 9bcbdd9c
      Arjan van de Ven authored 
      Now that range timers and deferred timers are common, I found a
problem with these using the "perf timechart" tool. Frans Pop also
reported high scheduler latencies via LatencyTop, when using
iwlagn.

It turns out that on x86, these two 'opportunistic' timers only get
checked when another "real" timer happens. These opportunistic
timers have the objective to save power by hitchhiking on other
wakeups, as to avoid CPU wakeups by themselves as much as possible.

The change in this patch runs this check not only at timer
interrupts, but at all (device) interrupts. The effect is that:

 1) the deferred timers/range timers get delayed less

 2) the range timers cause less wakeups by themselves because
    the percentage of hitchhiking on existing wakeup events goes up.

I've verified the working of the patch using "perf timechart", the
original exposed bug is gone with this patch. Frans also reported
success - the latencies are now down in the expected ~10 msec
range.
Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Tested-by: default avatarFrans Pop <elendil@planet.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20091008064041.67219b13@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      9bcbdd9c
  3. 07 Oct, 2009 1 commit
    • Eero Nurkkala's avatar
      NOHZ: update idle state also when NOHZ is inactive · fdc6f192
      Eero Nurkkala authored 
      Commit f2e21c96 had unfortunate side
effects with cpufreq governors on some systems.

If the system did not switch into NOHZ mode ts->inidle is not set when
tick_nohz_stop_sched_tick() is called from the idle routine. Therefor
all subsequent calls from irq_exit() to tick_nohz_stop_sched_tick()
fail to call tick_nohz_start_idle(). This results in bogus idle
accounting information which is passed to cpufreq governors.

Set the inidle flag unconditionally of the NOHZ active state to keep
the idle time accounting correct in any case.

[ tglx: Added comment and tweaked the changelog ]
Reported-by: default avatarSteven Noonan <steven@uplinklabs.net>
Signed-off-by: default avatarEero Nurkkala <ext-eero.nurkkala@nokia.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Greg KH <greg@kroah.com>
Cc: Steven Noonan <steven@uplinklabs.net>
Cc: stable@kernel.org
LKML-Reference: <1254907901.30157.93.camel@eenurkka-desktop>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      fdc6f192
  5. 05 Oct, 2009 15 commits
  7. 04 Oct, 2009 23 commits