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runtime: let sysmon sleep in netpoll if possible #51651
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156 changes: 156 additions & 0 deletions
src/runtime/sysmon_test.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,156 @@ | ||
| // Copyright 2022 The Go Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
|
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||
| // Test netpoll waiters G's will be unparked as soon as IO readied | ||
| // even though M's are busy with G's in local runq. | ||
|
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| package runtime_test | ||
|
|
||
| import ( | ||
| "net" | ||
| "runtime" | ||
| "testing" | ||
| "time" | ||
| ) | ||
|
|
||
| type busysrv struct { | ||
| l net.Listener | ||
| bucket []int | ||
| bucketTotal int | ||
| exit chan struct{} | ||
| start, end time.Time | ||
| } | ||
|
|
||
| func (srv *busysrv) stop() { | ||
| close(srv.exit) | ||
| } | ||
|
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| func (srv *busysrv) startListening() { | ||
| l, _ := net.Listen("tcp4", "localhost:0") | ||
| bucket := make([]int, 12) | ||
| exit := make(chan struct{}) | ||
| srv.l = l | ||
| srv.bucket = bucket | ||
| srv.exit = exit | ||
| go func() { | ||
| for { | ||
| select { | ||
| case _, ok := <-exit: | ||
| if !ok { | ||
| l.Close() | ||
| return | ||
| } | ||
| default: | ||
| } | ||
|
|
||
| if con, _ := l.Accept(); con != nil { | ||
| con.Close() | ||
| } | ||
| } | ||
| }() | ||
| } | ||
|
|
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| func (srv *busysrv) startDialing() { | ||
| srv.start = time.Now() | ||
| defer func() { | ||
| srv.end = time.Now() | ||
| }() | ||
| network, addr := srv.l.Addr().Network(), srv.l.Addr().String() | ||
| for { | ||
| select { | ||
| case _, ok := <-srv.exit: | ||
| if !ok { | ||
| return | ||
| } | ||
| default: | ||
| } | ||
|
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| start := time.Now() | ||
| con, _ := net.Dial(network, addr) | ||
| ms := int(time.Since(start) / 1000000) | ||
| if ms >= len(srv.bucket) { | ||
| ms = len(srv.bucket) - 1 | ||
| } | ||
| srv.bucket[ms]++ | ||
| srv.bucketTotal++ | ||
| if con != nil { | ||
| con.Close() | ||
| } | ||
| } | ||
| } | ||
|
|
||
| func (srv *busysrv) busy() { | ||
| for { | ||
| select { | ||
| case _, ok := <-srv.exit: | ||
| if !ok { | ||
| return | ||
| } | ||
| default: | ||
| } | ||
| runtime.Goyield() // simulate many runnable G's in local runq. | ||
| } | ||
| } | ||
|
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| func (srv *busysrv) expect(bucket int, percent float64) bool { | ||
| count := 0 | ||
| for i := 0; i < bucket && i < len(srv.bucket); i++ { | ||
| count += srv.bucket[i] | ||
| } | ||
| return float64(count)/float64(srv.bucketTotal)*100.0 > percent | ||
| } | ||
|
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| func (srv *busysrv) printf(ffn func(format string, args ...interface{})) { | ||
| ffn("dialed %d times within %v", srv.bucketTotal, srv.end.Sub(srv.start)) | ||
| ffn("timeBucket\tcount\tpercent") | ||
| for bucket, cnt := range srv.bucket { | ||
| percent := float64(cnt) / float64(srv.bucketTotal) * 100.0 | ||
| if bucket == len(srv.bucket)-1 { | ||
| ffn("[%2d, ~)ms\t%d\t%.2f%%", bucket, cnt, percent) | ||
| } else { | ||
| ffn("[%2d,%2d)ms\t%d\t%.2f%%", bucket, bucket+1, cnt, percent) | ||
| } | ||
| } | ||
| } | ||
|
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||
| func TestSysmonReadyNetpollWaitersASAP(t *testing.T) { | ||
| if runtime.GOOS == "netbsd" && runtime.NeedSysmonWorkaround { | ||
| t.Skip("netbsd 9.2 earlier") | ||
| } | ||
| if runtime.GOARCH == "wasm" { | ||
| t.Skip("no sysmon on wasm yet") | ||
| } | ||
| if runtime.GOOS == "openbsd" { | ||
| // usleep(20us) actually slept 20ms. see issue #17712. | ||
| t.Skip("sysmon may oversleep on openbsd.") | ||
| } | ||
|
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| // sysmon may starve if host load is too high. | ||
| np := runtime.GOMAXPROCS(0) | ||
| if np >= runtime.NumCPU() { | ||
| t.Skip("host load may be too high to run sysmon.") | ||
| } | ||
|
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||
| srv := &busysrv{} | ||
| srv.startListening() | ||
| for i := 0; i < np*5; i++ { | ||
| go srv.busy() | ||
| } | ||
| go srv.startDialing() | ||
|
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| time.Sleep(time.Second) | ||
| srv.stop() | ||
| time.Sleep(time.Millisecond * 100) | ||
|
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| // expect more than 80% dialings accomplished within 2ms in general. | ||
| // but android emulator may be slow, so more patience needed. | ||
| bucket, percent := 2, 80.0 | ||
| if runtime.GOOS == "android" { | ||
| bucket = 9 | ||
| } | ||
| if !srv.expect(bucket, percent) { | ||
| t.Fail() | ||
| } | ||
| srv.printf(t.Logf) | ||
| } |
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