On 26-Aug-2003 Yamada Ken Takeshi wrote: > JYI, > I tested machdep.hlt_logical_cpus=0/1, buildworld, > and found no particular reason to disable HTT > as below with Zeon 2.8Ghz x 2, 1GBmem, Slow IDE HDD. > > It may not be the common case, so just for your info. > ># sysctl machdep.hlt_logical_cpus=0 ># /usr/bin/time make -j32 buildworld > 1910.29 real 2520.53 user 777.30 sys > ># sysctl machdep.hlt_logical_cpus=1 ># /usr/bin/time make -j32 buildworld > 2289.33 real 2666.66 user 645.88 sys One test is not sufficient. -current is also not the best place to test. :) When I first implemented HTT in -current and -stable, I did some worldstone benchmarks on -stable on a machine with a single HTT CPU. Note that I was comparing a UP kernel with an SMP kernel as well, so some of the speed decrease of the SMP kernel could be due to it being an SMP kernel, not due to HTT. I did 16 trials (first one was throwaway) of back-to-back buildworlds of the same version of -stable using make, make -j2, and make -j4 for the following configurations: UP, HTT, HTT with smp_idle_hlt, and HTT with pause instructions added to stable and smp_idle_hlt. The fastest build time belonged to UP without any -j option. However, the next fastest ended up being the HTT with pause and smp_idle_hlt. The averages were 19:03 and 19:42 respectively with a standard deviation in both cases of around 3.5 seconds. That is only with 15 real trials though, so I'm not sure what kind of 90% confidence interval you would get from that. I did find that with the hlt and pause additions, the HTT kernel did complete the -j2 and -j4 builds faster than the UP kernel, but those builds still took longer than a build without -j. I can't remember if I committed the addition of the pause instructions to stable or not. If I didn't then I really should do that prior to 4.9. -- John Baldwin <jhb_at_FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/Received on Tue Aug 26 2003 - 09:14:59 UTC
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