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unix: avoid extra syscall on send/recvmsg on Linux

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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>
This commit is contained in:
Jason A. Donenfeld
2018-04-19 22:20:23 +00:00
committed by Brad Fitzpatrick
parent 3ccc7e5779
commit a2a45943ae
1 changed files with 22 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files
unix/syscall_linux.go
+22 -18
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@@ -944,15 +944,17 @@ func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from
} }
var dummy byte var dummy byte
if len(oob) > 0 { if len(oob) > 0 {
var sockType int if len(p) == 0 {
sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE) var sockType int
if err != nil { sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
return if err != nil {
} return
// receive at least one normal byte }
if sockType != SOCK_DGRAM && len(p) == 0 { // receive at least one normal byte
iov.Base = &dummy if sockType != SOCK_DGRAM {
iov.SetLen(1) iov.Base = &dummy
iov.SetLen(1)
}
} }
msg.Control = &oob[0] msg.Control = &oob[0]
msg.SetControllen(len(oob)) msg.SetControllen(len(oob))
@@ -996,15 +998,17 @@ func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error)
} }
var dummy byte var dummy byte
if len(oob) > 0 { if len(oob) > 0 {
var sockType int if len(p) == 0 {
sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE) var sockType int
if err != nil { sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
return 0, err if err != nil {
} return 0, err
// send at least one normal byte }
if sockType != SOCK_DGRAM && len(p) == 0 { // send at least one normal byte
iov.Base = &dummy if sockType != SOCK_DGRAM {
iov.SetLen(1) iov.Base = &dummy
iov.SetLen(1)
}
} }
msg.Control = &oob[0] msg.Control = &oob[0]
msg.SetControllen(len(oob)) msg.SetControllen(len(oob))