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syscall: 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: Id85cff17328ecbf6d09dd52fbeeaa691dbe69b75
Reviewed-on: https://go-review.googlesource.com/108338
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 23:46:52 +02:00 committed by Brad Fitzpatrick
parent 1c439e6e37
commit 68c10286c7
1 changed files with 22 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
src/syscall/syscall_linux.go
View File

@ -541,15 +541,17 @@ func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from
}
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))
@ -593,15 +595,17 @@ func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error)
}
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))