Messages in this thread | | | Date | Thu, 29 May 2008 13:29:15 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 2.6.26-rc3 : schedule] remove unlikely macros in workqueue.c/queue_delayed_work_on |
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On Thu, 29 May 2008 00:02:50 -0700 (PDT) youquan_song@linux.intel.com wrote:
> cpufreq_ondemand governor call queue_delayed_work_on with entry parameter > "cpu" every sample rate(every logical cpu during 20ms).check the value of > "cpu","cpu>=0" condition meeting rate is over than 90%. > > This patch remove the unlikely macros to benefit kernel schedule and > reader comprehension. > > Signed-off-by: Youquan Song <youquan.song@intel.com> > --- > workqueue.c | 2++++++ > 1 file changed, 1 insertions(+), 1 deletions(-) > > --- linux-2.6/kernel/workqueue.c 2008-05-13 10:10:11.000000000 -0400 > +++ linux-2.6-new/kernel/workqueue.c 2008-05-29 09:46:16.000000000 -0400 > @@ -230,7 +230,7 @@ > timer->data = (unsigned long)dwork; > timer->function = delayed_work_timer_fn; > > - if (unlikely(cpu >= 0)) > + if (cpu >= 0) > add_timer_on(timer, cpu); > else > add_timer(timer); >
This is very much dependent on what workload the machine is running.
There are 189 queue_delayed_work() callsites and they all want the unlikely() to be there.
There are six queue_delayed_work_on() callsites and they don't want the unlikely().
Don't know what to do here. Fortunately it doesn't matter much ;)
-mm has profile-likely-unlikely-macros.patch which can be used to instrument these things (that feature seems to get broken regularly though).
But the instrumentation should be performed across a broad range of workloads.
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