linux-kernel - Re: [PATCH V3]hrtimer: Fix a performance regression by disable reprogramming in remove

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Date:	Fri, 4 Oct 2013 20:06:55 +0800
From:	Ethan Zhao <ethan.kernel@...il.com>
To:	Mike Galbraith <bitbucket@...ine.de>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>, rjw@...k.pl,
	daniel.lezcano@...aro.org, linux-pm@...r.kernel.org,
	lenb@...nel.org
Subject: Re: [PATCH V3]hrtimer: Fix a performance regression by disable
 reprogramming in remove_hrtimer

Mike, Peter,
   Seems lots of work has been done these days, studious guys. those
patches merged in last stable/dev branch (fix performance regression
caused by extra rtimer programming and rescheduling IPI,confusing
idle... etc) ? So I could just do a lazy pull for test with my
environment.  I need catch up with other mail loops with my vacation
again.

Thanks,
Ethan

On Wed, Sep 11, 2013 at 6:25 PM, Mike Galbraith <bitbucket@...ine.de> wrote:
> On Wed, 2013-09-11 at 10:56 +0200, Peter Zijlstra wrote:
>> On Mon, Sep 09, 2013 at 03:46:35PM +0200, Peter Zijlstra wrote:
>> > On Mon, Sep 09, 2013 at 03:30:44PM +0200, Peter Zijlstra wrote:
>> > > diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
>> > > index fa6964d..486c0ba 100644
>> > > --- a/drivers/idle/intel_idle.c
>> > > +++ b/drivers/idle/intel_idle.c
>> > > @@ -359,6 +359,14 @@ static int intel_idle(struct cpuidle_device *dev,
>> > >   if (!(lapic_timer_reliable_states & (1 << (cstate))))
>> > >           clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
>> > >
>> > > + current_thread_into()->status |= TS_POLLING;
>> > > +
>> > > + /*
>> > > +  * Order against setting of TS_POLLING against the reading of
>> > > +  * NEED_RESCHED, matched by resched_task().
>> > > +  */
>> > > + smp_mb();
>> > > +
>> > >   if (!need_resched()) {
>> > >
>> > >           __monitor((void *)&current_thread_info()->flags, 0, 0);
>> > > @@ -367,6 +375,8 @@ static int intel_idle(struct cpuidle_device *dev,
>> > >                   __mwait(eax, ecx);
>> > >   }
>> > >
>> > > + current_thread_into()->status &= ~TS_POLLING;
>> > > +
>> > >   if (!(lapic_timer_reliable_states & (1 << (cstate))))
>> > >           clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
>> >
>> > Hmm, arguably it would be better to set this from
>> > intel_idle_cpuidle_driver_init() and clear it whenever this goes away.
>> > Not sure how all that works, the cpuidle driver framework seems 'weird'.
>>
>> OK, so I went over the idle stuff again, and we do set TS_POLLING like
>> stuff, it got hidden in current_{clr,set}_polling().
>>
>> Still if that patch causes extra IPIs its bound to be broken in some
>> creative way.. I'll prod.
>
> (thanks, when I get a break from testing/poking this'n'that, I'll take a
> peek too...  well, good_intentions++ anyway;)
>
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