Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754079Ab3IINay (ORCPT ); Mon, 9 Sep 2013 09:30:54 -0400 Received: from merlin.infradead.org ([205.233.59.134]:50767 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753218Ab3IINaw (ORCPT ); Mon, 9 Sep 2013 09:30:52 -0400 Date: Mon, 9 Sep 2013 15:30:44 +0200 From: Peter Zijlstra To: Mike Galbraith Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Thomas Gleixner , ethan.kernel@gmail.com Subject: Re: [PATCH V3]hrtimer: Fix a performance regression by disable reprogramming in remove_hrtimer Message-ID: <20130909133044.GB31370@twins.programming.kicks-ass.net> References: <20130729115701.GD3008@twins.programming.kicks-ass.net> <24EECBCC-F655-404F-8946-73CC36095A5F@gmail.com> <1378362989.18435.2.camel@marge.simpson.net> <20130905111428.GB23362@gmail.com> <1378386697.6567.9.camel@marge.simpson.net> <20130905133750.GA26637@gmail.com> <1378445942.5434.31.camel@marge.simpson.net> <20130909122325.GX31370@twins.programming.kicks-ass.net> <1378730538.5586.30.camel@marge.simpson.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1378730538.5586.30.camel@marge.simpson.net> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2406 Lines: 67 Lets go back to the list with this.. On Mon, Sep 09, 2013 at 02:42:18PM +0200, Mike Galbraith wrote: > On Mon, 2013-09-09 at 14:23 +0200, Peter Zijlstra wrote: > > On Fri, Sep 06, 2013 at 07:39:02AM +0200, Mike Galbraith wrote: > > > The patch takes a large bite out of regressions. What's left for a > > > Westmere box is the introduction of reschedule_interrupt overhead > > > introduced by 7d1a9417 x86: Use generic idle loop. > > > > How exactly does that commit cause extra IPIs? Did the entire TS_POLLING > > stuff break or so? > > Seems so. > > > > Core2 eats that, > > > plus Intel making mwait_idle() go away with no way for them to get to > > > the remaining mwait_idle_with_hints(). > > > > but but but drivers/idle/intel_idle.c still uses mwait.. what's the > > exact complaint? > > reschedule_interrupt overhead for cross core pipe-test appeared in > westmere box at 7d1a9417. So that patch does indeed loose the TS_POLLING stuff for all of x86. I'm not entirely sure where we want to add it back, but the best place to me seems the idle loop implementations themselves. Below a patch that does intel_idle.c which is what your WSM would be using I suppose. We'll probably want to iterate all idle implementations and do what needs doing. --- 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 *)¤t_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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/