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Message-ID: <20071120085704.GA19950@elte.hu> Date: Tue, 20 Nov 2007 09:57:04 +0100 From: Ingo Molnar <mingo@...e.hu> To: Pavel Machek <pavel@....cz> Cc: kernel list <linux-kernel@...r.kernel.org>, tglx@...utronix.de Subject: Re: nohz and strange sleep latencies * Pavel Machek <pavel@....cz> wrote: > > > 0.00user 0.00system 0.08 (0m0.081s) elapsed 3.71%CPU > > > 0.00user 0.00system 0.01 (0m0.013s) elapsed 23.33%CPU > > > 0.00user 0.00system 0.01 (0m0.019s) elapsed 15.92%CPU > > > > > > nohz=off helps a lot. while true; do time sleep 0.0; done does not > > > have unexpected latencies. > > > > does hpet=disable on the boot line also help? (without nohz=off) > > hpet-disable helps.. a bit. 200msec latencies are gone. (What is used > for wakeups in this case?) > > pavel@amd:~$ while true; do time sleep 0.01; done > 0.00user 0.00system 0.01 (0m0.013s) elapsed 22.96%CPU > 0.00user 0.00system 0.01 (0m0.018s) elapsed 11.05%CPU > 0.00user 0.00system 0.01 (0m0.013s) elapsed 15.54%CPU could you run this while doing the sleep test: http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh and send us the output? (Enabling CONFIG_TIMER_STATS, CONFIG_SCHED_DEBUG and CONFIG_SCHEDSTATS would maximize the amount of information.) 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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