Date: Sun, 25 Jul 2010 02:06:50 +0300 From: Alexander Motin <mav@FreeBSD.org> To: Rui Paulo <rpaulo@lavabit.com> Cc: freebsd-hackers@freebsd.org, freebsd-performance@freebsd.org Subject: Re: Intel TurboBoost in practice Message-ID: <4C4B720A.6020802@FreeBSD.org> In-Reply-To: <A30A636F-E925-456E-8866-4E46B3BA367F@lavabit.com> References: <4C4AF046.40507@FreeBSD.org> <A30A636F-E925-456E-8866-4E46B3BA367F@lavabit.com>
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Rui Paulo wrote: > On 24 Jul 2010, at 14:53, Alexander Motin wrote: >> 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). >> >> Untuned system (hz=1000): 14.15 sec >> Enabled ACPI C2 (hz=1000+C2): 13.85 sec >> Enabled ACPI C3 (hz=1000+C3): 13.91 sec >> Reduced HZ (hz=100): 14.16 sec >> Enabled ACPI C2 (hz=100+C2): 13.85 sec >> Enabled ACPI C3 (hz=100+C3): 13.86 sec >> Timers tuned* (hz=100): 14.10 sec >> Enabled ACPI C2 (hz=100+C2): 13.71 sec >> Enabled ACPI C3 (hz=100+C3): 13.73 sec >> >> All numbers tested few times and are repeatable up to +/-0.01sec. >> >> 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? If you mean relative difference -- as I have told, it's mostly because of my CPU. It's maximal boost is 266MHz (8.3%), but 133MHz of them is enabled most of time if CPU is not overheated. It probably doesn't, as it works on clear table under air conditioner. So maximal effect I can expect on is 4.2%. In such situation 2.8% probably not so bad to illustrate that feature works and there is space for further improvements. If I had Core i5-750S I would expect 33% boost. If you mean absolute difference, here are results or four buildworld runs: hw.acpi.cpu.cx_lowest=C1: 4654.23 sec hw.acpi.cpu.cx_lowest=C2: 4556.37 sec hw.acpi.cpu.cx_lowest=C2: 4570.85 sec hw.acpi.cpu.cx_lowest=C1: 4679.83 sec Benefit is about 2.1%. Each time results were erased and sources pre-cached into RAM. Storage was SSD, so disk should not be an issue. -- Alexander Motin
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