On Tue, Jun 28, 2016 at 02:43:36PM +0200, Peter Zijlstra wrote: > On Fri, Jun 17, 2016 at 12:43:22PM -0500, Josh Poimboeuf wrote: > > NOTE: I didn't include any performance numbers because I wasn't able to > > get consistent results. I tried the following on a Xeon E5-2420 v2 CPU: > > > > $ for i in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do echo > > -n performance > $i; done > > $ echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo > > $ echo 100 > /sys/devices/system/cpu/intel_pstate/min_perf_pct > > $ echo 0 > /proc/sys/kernel/nmi_watchdog > > $ taskset 0x10 perf stat -n -r10 perf bench sched pipe -l 1000000 > > > > I was going to post the numbers from that, both with and without > > SCHEDSTATS, but then when I tried to repeat the test on a different day, > > the results were surprisingly different, with different conclusions. > > > > So any advice on measuring scheduler performance would be appreciated... > > Yeah, its a bit of a pain in general... > > A) perf stat --null --repeat 50 -- perf bench sched messaging -g 50 -l 5000 | > grep "seconds time elapsed" > B) perf stat --null --repeat 50 -- taskset 1 perf bench sched pipe | grep > "seconds time elapsed" > > 1) tip/master + 1-4 > 2) tip/master + 1-5 > 3) tip/master + 1-5 + below > > 1 2 3 > > A) 4.627767855 4.650429917 4.646208062 > 4.633921933 4.641424424 4.612021058 > 4.649536375 4.663144144 4.636815948 > 4.630165619 4.649053552 4.613022902 > > B) 1.770732957 1.789534273 1.773334291 > 1.761740716 1.795618428 1.773338681 > 1.763761666 1.822316496 1.774385589 > > > From this it looks like patch 5 does hurt a wee bit, but we can get most > of that back by reordering the structure a bit. The results seem > 'stable' across rebuilds and reboots (I've pop'ed all patches and > rebuild, rebooted and re-benched 1 at the end and obtained similar > results). > > Although, possible that if we reorder first and then do 5, we'll just > see a bigger regression. I've not bothered.
Thanks a lot for benchmarking this! And also for improving the cache alignments. Your changes look good to me. -- Josh
