Date: Sat, 24 Jul 2010 17:18:53 +0100 From: Rui Paulo <rpaulo@lavabit.com> To: Alexander Motin <mav@FreeBSD.org> Cc: freebsd-hackers@freebsd.org, freebsd-performance@freebsd.org Subject: Re: Intel TurboBoost in practice Message-ID: <A30A636F-E925-456E-8866-4E46B3BA367F@lavabit.com> In-Reply-To: <4C4AF046.40507@FreeBSD.org> References: <4C4AF046.40507@FreeBSD.org>
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On 24 Jul 2010, at 14:53, Alexander Motin wrote: > Hi. >=20 > I've make small observations of Intel TurboBoost technology under > FreeBSD. This technology allows Intel Core i5/i7 CPUs to rise = frequency > of some cores if other cores are idle and power/thermal conditions > permit. CPU core counted as idle, if it has been put into C3 or deeper > power state (may reflect ACPI C2/C3 states). So to reach maximal > effectiveness, some tuning may be needed. >=20 > Here is my test case: FreeBSD 9-CURRENT on Core i5 650 CPU, 3.2GHz + = 1/2 > TurboBoost steps (+133/+266MHz) with boxed cooler at the open air. I = was > measuring building time of the net/mpd5 from sources, using only one = CPU > core (cpuset -l 0 time make). >=20 > Untuned system (hz=3D1000): 14.15 sec > Enabled ACPI C2 (hz=3D1000+C2): 13.85 sec > Enabled ACPI C3 (hz=3D1000+C3): 13.91 sec > Reduced HZ (hz=3D100): 14.16 sec > Enabled ACPI C2 (hz=3D100+C2): 13.85 sec > Enabled ACPI C3 (hz=3D100+C3): 13.86 sec > Timers tuned* (hz=3D100): 14.10 sec > Enabled ACPI C2 (hz=3D100+C2): 13.71 sec > Enabled ACPI C3 (hz=3D100+C3): 13.73 sec >=20 > All numbers tested few times and are repeatable up to +/-0.01sec. >=20 > *) Timers were tuned to reduce interrupt rates and respectively = increase > idle cores sleep time. These lines were added to loader.conf: > sysctl kern.eventtimer.timer1=3Di8254 > sysctl kern.eventtimer.timer2=3DNONE > kern.eventtimer.singlemul=3D1 > kern.hz=3D"100" >=20 > PS: In this case benefit is small, but it is the least that can be > achieved, depending on CPU model. Some models allow frequency to be > risen by up to 6 steps (+798MHz). The numbers that you are showing doesn't show much difference. Have you = tried buildworld? >=20 > PPS: I expect even better effect achieved by further reducing = interrupt > rates on idle CPUs. >=20 > --=20 > Alexander Motin > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to = "freebsd-hackers-unsubscribe@freebsd.org" >=20 > = __________________________________________________________________________= __________ > Use the link below to report this message as spam. > https://lavabit.com/apps/teacher?sig=3D1225540&key=3D3283483970 > = __________________________________________________________________________= __________ Regards, -- Rui Paulo
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