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Message-ID: <20090213082223.GA4606@elte.hu> Date: Fri, 13 Feb 2009 09:22:23 +0100 From: Ingo Molnar <mingo@...e.hu> To: Michael Davidson <md@...gle.com> Cc: mbligh@...gle.com, tglx@...utronix.de, linux-kernel@...r.kernel.org Subject: Re: [PATCH] clockevents: avoid unnecessary reprograming of event timer * Michael Davidson <md@...gle.com> wrote: > From: Michael Davidson <md@...gle.com> > > Don't reprogram the event timer if it is already set to expire > at the correct time. > > Signed-off-by: Michael Davidson <md@...gle.com> > --- > --- linux-2.6.29-rc4.orig/kernel/time/clockevents.c 2009-02-12 13:13:24.000000000 -0800 > +++ linux-2.6.29-rc4/kernel/time/clockevents.c 2009-02-12 13:25:42.525558000 -0800 > @@ -103,6 +103,9 @@ > if (delta <= 0) > return -ETIME; > > + if (ktime_equal(dev->next_event, expires)) > + return 0; > + Hm, given that a good high-res source has nanoseconds resolution, what's the chance of this optimization triggering in practice? Near zero i think - unless we trigger useless reprogramming without having added or removed any new timers - but then we should concentrate on analyzing the reason for that redundant reprogramming. Does it trigger often for you? Ingo -- 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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