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_freebsd.go b/src/pkg/net/sendfile_freebsd.go
index dc5b767..42fe799 100644
--- a/src/pkg/net/sendfile_freebsd.go
+++ b/src/pkg/net/sendfile_freebsd.go
@@ -58,12 +58,10 @@
return 0, err, false
}
- c.wio.Lock()
- defer c.wio.Unlock()
- if err := c.incref(false); err != nil {
+ if err := c.writeLock(); err != nil {
return 0, err, true
}
- defer c.decref()
+ defer c.writeUnlock()
dst := c.sysfd
src := int(f.Fd())
