Messages in this thread | | | Date | Thu, 29 May 2008 15:50:36 -0700 | From | Arjan van de Ven <> | 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 13:29:15 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:
> 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.
and on x86 it barely makes any difference at all, at best you can handwave a little about icache footprint.
/me ponders checking if we get a code size reduction by defining these animals to be empty passthrough
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