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). PPS: I expect even better effect achieved by further reducing interrupt rates on idle CPUs. -- Alexander Motin _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
