unix: avoid extra syscall on send/recvmsg on Linux
By simply rearranging the logic, we avoid the overhead of a superfluous
call to getsockopt. For, if p is already non empty, there's no point
in having to check if we need to attach dummy payload. This has
performance benefits when using send/recvmsg for high speed
communications.
Change-Id: If47ab5322464aad8e6d2603a369e95327223211f
Reviewed-on: https://go-review.googlesource.com/108337
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/unix/syscall_linux.go b/unix/syscall_linux.go
index 56306ac..04f38c5 100644
--- a/unix/syscall_linux.go
+++ b/unix/syscall_linux.go
@@ -944,15 +944,17 @@
}
var dummy byte
if len(oob) > 0 {
- var sockType int
- sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
- if err != nil {
- return
- }
- // receive at least one normal byte
- if sockType != SOCK_DGRAM && len(p) == 0 {
- iov.Base = &dummy
- iov.SetLen(1)
+ if len(p) == 0 {
+ var sockType int
+ sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
+ if err != nil {
+ return
+ }
+ // receive at least one normal byte
+ if sockType != SOCK_DGRAM {
+ iov.Base = &dummy
+ iov.SetLen(1)
+ }
}
msg.Control = &oob[0]
msg.SetControllen(len(oob))
@@ -996,15 +998,17 @@
}
var dummy byte
if len(oob) > 0 {
- var sockType int
- sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
- if err != nil {
- return 0, err
- }
- // send at least one normal byte
- if sockType != SOCK_DGRAM && len(p) == 0 {
- iov.Base = &dummy
- iov.SetLen(1)
+ if len(p) == 0 {
+ var sockType int
+ sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
+ if err != nil {
+ return 0, err
+ }
+ // send at least one normal byte
+ if sockType != SOCK_DGRAM {
+ iov.Base = &dummy
+ iov.SetLen(1)
+ }
}
msg.Control = &oob[0]
msg.SetControllen(len(oob))
