On 09/19/10 06:57, Alexander Motin wrote:
Getting back to that topic I would like to share some more results. This time I was testing Core(TM) i7 870 @ 2.93GHz. It has 8 logical cores and bigger allowed TurboBoost effect. I was testing real time of net/mpd5 port building, using single CPU. I was testing it with HZ=1000 with different C-states allowed and with/without kern.eventtimer.idletick sysctl enabled (supported by the latest event timer code in HEAD). This sysctl, when disabled, allows to avoid most of timer interrupts on idle cores, allowing them to sleep deeper.
If I understand correctly, TurboBoost is supposed to increase the frequency of one or a small number of cores only?
What is the physical increase in frequency on this CPU when TurboBoost is enabled?
As you may see, with full timer interrupt rate TurboBoost effect (part of it, that enabled by some number of idle cores) is about 3-4%. CPUs are not sleeping long enough. But without extra interrupts on idle cores effect increasing to more then 10%!
Is this interpretation correct: when building with single core (-j1 effectively), using TurboBoost with the new code is >10% faster than without TurboBoost?
Does it have any effect if you try using all the cores? _______________________________________________ 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"
