On Monday, 8 May 2006 at 21:11:09 -0400, Kris Kennaway wrote: > On Mon, May 08, 2006 at 08:43:28PM -0400, Kris Kennaway wrote: >> On Mon, May 08, 2006 at 02:52:07AM -0400, Kris Kennaway wrote: >>> OK, David's patch fixes the umtx thundering herd (and seems to give a >>> 4-6% boost). I also fixed a thundering herd in FILEDESC_UNLOCK (which >>> was also waking up 2-7 CPUs at once about 30% of the time) by doing >>> s/wakeup/wakeup_one/. This did not seem to give a performance impact >>> on this test though. >> >> Turning down kern.hz from 1000 to 100 also made a big difference on 12 >> CPUs (+6.1%). >> >> Note also that the system is no less than 40% idle during the runs (at >> any load), so the bottlenecks are serious. > > top -H shows the threads mostly in umtx state. This doesn't lend much support to the idea that the gettimeofday() calls are a bottleneck. I've just been through the code, but if there are any mutexes acquired there, I missed them. Greg -- See complete headers for address and phone numbers
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