• Dmitry Vyukov's avatar
    runtime: remove unnecessary wakeups of worker threads · fb6f8a96
    Dmitry Vyukov authored
    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/17540Reviewed-by: 's avatarAustin Clements <austin@google.com>
    Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    fb6f8a96
proc_test.go 13.2 KB