net: add special netFD mutex
The mutex, fdMutex, handles locking and lifetime of sysfd,
and serializes Read and Write methods.
This allows to strip 2 sync.Mutex.Lock calls,
2 sync.Mutex.Unlock calls, 1 defer and some amount
of misc overhead from every network operation.
On linux/amd64, Intel E5-2690:
benchmark old ns/op new ns/op delta
BenchmarkTCP4Persistent 9595 9454 -1.47%
BenchmarkTCP4Persistent-2 8978 8772 -2.29%
BenchmarkTCP4ConcurrentReadWrite 4900 4625 -5.61%
BenchmarkTCP4ConcurrentReadWrite-2 2603 2500 -3.96%
In general it strips 70-500 ns from every network operation depending
on processor model. On my relatively new E5-2690 it accounts to ~5%
of network op cost.
Fixes #6074.
R=golang-dev, bradfitz, alex.brainman, iant, mikioh.mikioh
CC=golang-dev
https://golang.org/cl/12418043
diff --git a/src/pkg/net/sendfile_windows.go b/src/pkg/net/sendfile_windows.go
index e9b9f91..0107f67 100644
--- a/src/pkg/net/sendfile_windows.go
+++ b/src/pkg/net/sendfile_windows.go
@@ -34,13 +34,12 @@
return 0, nil, false
}
- if err := fd.incref(false); err != nil {
+ if err := fd.writeLock(); err != nil {
return 0, err, true
}
- defer fd.decref()
+ defer fd.writeUnlock()
+
o := &fd.wop
- o.mu.Lock()
- defer o.mu.Unlock()
o.qty = uint32(n)
o.handle = syscall.Handle(f.Fd())
done, err := iosrv.ExecIO(o, "TransmitFile", func(o *operation) error {
