Messages in this thread | | | From | Andrei Vagin <> | Date | Mon, 31 Oct 2022 15:37:21 -0700 | Subject | Re: [PATCH] sched: consider WF_SYNC to find idle siblings |
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On Mon, Oct 31, 2022 at 5:57 AM Peter Zijlstra <peterz@infradead.org> wrote: > > On Thu, Oct 27, 2022 at 01:26:03PM -0700, Andrei Vagin wrote: > > From: Andrei Vagin <avagin@gmail.com> > > > > WF_SYNC means that the waker goes to sleep after wakeup, so the current > > cpu can be considered idle if the waker is the only process that is > > running on it. > > > > The perf pipe benchmark shows that this change reduces the average time > > per operation from 8.8 usecs/op to 3.7 usecs/op. > > > > Before: > > $ ./tools/perf/perf bench sched pipe > > # Running 'sched/pipe' benchmark: > > # Executed 1000000 pipe operations between two processes > > > > Total time: 8.813 [sec] > > > > 8.813985 usecs/op > > 113456 ops/sec > > > > After: > > $ ./tools/perf/perf bench sched pipe > > # Running 'sched/pipe' benchmark: > > # Executed 1000000 pipe operations between two processes > > > > Total time: 3.743 [sec] > > > > 3.743971 usecs/op > > 267096 ops/sec > > But what; if anything, does it do for the myrad of other benchmarks we > run?
I've run these set of benchmarks: * perf bench sched messaging * perf bench epoll all * perf bench futex all * schbench * tbench * kernel compilation
Results look the same with and without this change for all benchmarks except tbench. tbench shows improvements when a number of processes is less than a number of cpu-s.
Here are results from my test host with 8 cpu-s.
$ tbench_srv & "tbench" "-t" "15" "1" "127.0.0.1" Before: Throughput 260.498 MB/sec 1 clients 1 procs max_latency=1.301 ms After: Throughput 462.047 MB/sec 1 clients 1 procs max_latency=1.066 ms
$ tbench_srv & "tbench" "-t" "15" "4" "127.0.0.1" Before: Throughput 733.44 MB/sec 4 clients 4 procs max_latency=0.935 ms After: Throughput 1778.94 MB/sec 4 clients 4 procs max_latency=0.882 ms
$ tbench_srv & "tbench" "-t" "15" "8" "127.0.0.1" Before: Throughput 1965.41 MB/sec 8 clients 8 procs max_latency=2.145 ms After: Throughput 2002.96 MB/sec 8 clients 8 procs max_latency=1.881 ms
$ tbench_srv & "tbench" "-t" "15" "32" "127.0.0.1" Before: Throughput 1881.79 MB/sec 32 clients 32 procs max_latency=16.365 ms After: Throughput 1891.87 MB/sec 32 clients 32 procs max_latency=4.050 ms
Let me know if you want to see results for any other specific benchmark.
Thanks, Andrei
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