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Message-ID: <20090722180248.57e31f20@skybase> Date: Wed, 22 Jul 2009 18:02:48 +0200 From: Martin Schwidefsky <schwidefsky@...ibm.com> To: Thomas Gleixner <tglx@...utronix.de> Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>, john stultz <johnstul@...ibm.com>, Venki Pallipadi <venkatesh.pallipadi@...el.com> Subject: Re: [RFC][PATCH] cache __next_timer_interrupt result On Wed, 22 Jul 2009 16:38:18 +0200 (CEST) Thomas Gleixner <tglx@...utronix.de> wrote: > On Tue, 21 Jul 2009, Martin Schwidefsky wrote: > > > From: Martin Schwidefsky <schwidefsky@...ibm.com> > > > > Each time a cpu goes to sleep on a NOHZ=y system the timer wheel is > > searched for the next timer interrupt. It can take quite a few cycles > > to find the next pending timer. This patch adds a field to tvec_base > > that caches the result of __next_timer_interrupt. The hit ratio is > > around 80% on my thinkpad under normal use, on a server I've seen > > Nice, I like it. Thanks :-) > > hit ratios from 5% to 95% dependent on the workload. > > Which workloads result in lower hit ratios ? Heavy networking ? 5% ping-pong packet over loopback between two cpus. So yes, networking. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- 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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