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Date: Mon, 16 Nov 2015 16:09:10 -0800 From: Jacob Pan <jacob.jun.pan@...ux.intel.com> To: Thomas Gleixner <tglx@...utronix.de> Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, John Stultz <john.stultz@...aro.org>, LKML <linux-kernel@...r.kernel.org>, Arjan van de Ven <arjan@...ux.intel.com>, Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, Len Brown <len.brown@...el.com>, Rafael Wysocki <rafael.j.wysocki@...el.com>, Eduardo Valentin <edubezval@...il.com>, Paul Turner <pjt@...gle.com>, Josh Triplett <josh@...htriplett.org>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, jacob.jun.pan@...ux.intel.com Subject: Re: [PATCH 2/4] timer: relax tick stop in idle entry On Mon, 16 Nov 2015 23:01:12 +0100 (CET) Thomas Gleixner <tglx@...utronix.de> wrote: > > For the second case, which is much more rare, I think we do have > > next timer exactly one tick away. Just don't know why tick will > > continue into idle loop. > > Well, it should not be hard to figure that out. There are not so many > checks involved when tick_nohz_irq_exit() is called. Thanks for the tip, I found the cause is in int idle_cpu(int cpu) { if (rq->nr_running) return 0; Since we only take into account of cfs_rq runnable taking over cfs_rq->nr_running when forced_idle is set. Jacob -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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