On 24 Jul 2010, at 14:53, Alexander Motin wrote: > Hi. > > 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. > > 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. > > *) 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=i8254 > sysctl kern.eventtimer.timer2=NONE > kern.eventtimer.singlemul=1 > kern.hz="100" > > 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? > > PPS: I expect even better effect achieved by further reducing interrupt > rates on idle CPUs. > > -- > Alexander Motin > _______________________________________________ > freebsd-hack...@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org" > > ____________________________________________________________________________________ > Use the link below to report this message as spam. > https://lavabit.com/apps/teacher?sig=1225540&key=3283483970 > ____________________________________________________________________________________ Regards, -- Rui Paulo _______________________________________________ freebsd-performance@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscr...@freebsd.org"
