Re: [PATCH V3]hrtimer: Fix a performance regression by disablereprogramming in remove_hrtimer

From: Peter Zijlstra
Date: Tue Jul 30 2013 - 05:35:32 EST

On Tue, Jul 30, 2013 at 05:12:49PM +0800, Ethan Zhao wrote:
> On Mon, Jul 29, 2013 at 6:18 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> > The test case does not involve anything hrtimer related. Do you have
> >
> Yes. it is default configured in stable release.

Should still be disabled by default even if supported:

# grep HRTICK kernel/sched/features.h

> > First of all we want to know, which particular hrtimer is causing that
> > issue. If it is the hrtick one, then I really have to ask why you want
> > to use it at all in such a high performance scenario.
> >
> > Any advice about the HZ in high performance scenario ? hrtimer tick
> Is not fit for high performance ?

Hence why its disabled, programming the timer hardware is too expensive.
But since you didn't even know that I suspect you aren't in fact using

It would be good if you could do what Thomas suggested and look at which
timer is actually active during your workload.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at