runtime: remove unnecessary wakeups of worker threads
Currently we wake up new worker threads whenever we pass
through the scheduler with nmspinning==0. This leads to
lots of unnecessary thread wake ups.
Instead let only spinning threads wake up new spinning threads.
For the following program:
package main
import "runtime"
func main() {
for i := 0; i < 1e7; i++ {
runtime.Gosched()
}
}
Before:
$ time ./test
real 0m4.278s
user 0m7.634s
sys 0m1.423s
$ strace -c ./test
% time seconds usecs/call calls errors syscall
99.93 9.314936 3
2685009 17536 futex
After:
$ time ./test
real 0m1.200s
user 0m1.181s
sys 0m0.024s
$ strace -c ./test
% time seconds usecs/call calls errors syscall
3.11 0.000049 25 2 futex
Fixes #13527
Change-Id: Ia1f5bf8a896dcc25d8b04beb1f4317aa9ff16f74
Reviewed-on: https://go-review.googlesource.com/17540
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>