internal/poll: re-use RawSockaddrAny buffers across requests on windows

We were re-allocating a new RawSockaddrAny on every UDP read/write.
We can re-use them instead.

This reduces the number of allocs for UDP read/write on windows to zero.

Co-authored-by: David Crawshaw <crawshaw@golang.org>
Change-Id: I2f05c974e2e7b4f67937ae4e1c99583e81d140af
Reviewed-on: https://go-review.googlesource.com/c/go/+/361404
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/internal/poll/fd_windows.go b/src/internal/poll/fd_windows.go
index 94cdfca60163edf2222603f1509c79dfbf81d2db..0d8bf879921d2bcab93894bc8898a359373455c1 100644 (file)
--- a/src/internal/poll/fd_windows.go
+++ b/src/internal/poll/fd_windows.go
@@ -1116,25 +1116,27 @@ func (fd *FD) RawWrite(f func(uintptr) bool) error {
        return syscall.EWINDOWS
 }
 
-func sockaddrInet4ToRaw(sa *syscall.SockaddrInet4) (unsafe.Pointer, int32) {
-       var raw syscall.RawSockaddrInet4
+func sockaddrInet4ToRaw(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet4) int32 {
+       *rsa = syscall.RawSockaddrAny{}
+       raw := (*syscall.RawSockaddrInet4)(unsafe.Pointer(rsa))
        raw.Family = syscall.AF_INET
        p := (*[2]byte)(unsafe.Pointer(&raw.Port))
        p[0] = byte(sa.Port >> 8)
        p[1] = byte(sa.Port)
        raw.Addr = sa.Addr
-       return unsafe.Pointer(&raw), int32(unsafe.Sizeof(raw))
+       return int32(unsafe.Sizeof(*raw))
 }
 
-func sockaddrInet6ToRaw(sa *syscall.SockaddrInet6) (unsafe.Pointer, int32) {
-       var raw syscall.RawSockaddrInet6
+func sockaddrInet6ToRaw(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet6) int32 {
+       *rsa = syscall.RawSockaddrAny{}
+       raw := (*syscall.RawSockaddrInet6)(unsafe.Pointer(rsa))
        raw.Family = syscall.AF_INET6
        p := (*[2]byte)(unsafe.Pointer(&raw.Port))
        p[0] = byte(sa.Port >> 8)
        p[1] = byte(sa.Port)
        raw.Scope_id = sa.ZoneId
        raw.Addr = sa.Addr
-       return unsafe.Pointer(&raw), int32(unsafe.Sizeof(raw))
+       return int32(unsafe.Sizeof(*raw))
 }
 
 func rawToSockaddrInet4(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet4) {
@@ -1152,16 +1154,16 @@ func rawToSockaddrInet6(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet6)
        sa.Addr = pp.Addr
 }
 
-func sockaddrToRaw(sa syscall.Sockaddr) (unsafe.Pointer, int32, error) {
+func sockaddrToRaw(rsa *syscall.RawSockaddrAny, sa syscall.Sockaddr) (int32, error) {
        switch sa := sa.(type) {
        case *syscall.SockaddrInet4:
-               ptr, sz := sockaddrInet4ToRaw(sa)
-               return ptr, sz, nil
+               sz := sockaddrInet4ToRaw(rsa, sa)
+               return sz, nil
        case *syscall.SockaddrInet6:
-               ptr, sz := sockaddrInet6ToRaw(sa)
-               return ptr, sz, nil
+               sz := sockaddrInet6ToRaw(rsa, sa)
+               return sz, nil
        default:
-               return nil, 0, syscall.EWINDOWS
+               return 0, syscall.EWINDOWS
        }
 }
 
@@ -1178,7 +1180,9 @@ func (fd *FD) ReadMsg(p []byte, oob []byte, flags int) (int, int, int, syscall.S
 
        o := &fd.rop
        o.InitMsg(p, oob)
-       o.rsa = new(syscall.RawSockaddrAny)
+       if o.rsa == nil {
+               o.rsa = new(syscall.RawSockaddrAny)
+       }
        o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
        o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
        o.msg.Flags = uint32(flags)
@@ -1206,7 +1210,9 @@ func (fd *FD) ReadMsgInet4(p []byte, oob []byte, flags int, sa4 *syscall.Sockadd
 
        o := &fd.rop
        o.InitMsg(p, oob)
-       o.rsa = new(syscall.RawSockaddrAny)
+       if o.rsa == nil {
+               o.rsa = new(syscall.RawSockaddrAny)
+       }
        o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
        o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
        o.msg.Flags = uint32(flags)
@@ -1233,7 +1239,9 @@ func (fd *FD) ReadMsgInet6(p []byte, oob []byte, flags int, sa6 *syscall.Sockadd
 
        o := &fd.rop
        o.InitMsg(p, oob)
-       o.rsa = new(syscall.RawSockaddrAny)
+       if o.rsa == nil {
+               o.rsa = new(syscall.RawSockaddrAny)
+       }
        o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
        o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
        o.msg.Flags = uint32(flags)
@@ -1261,11 +1269,14 @@ func (fd *FD) WriteMsg(p []byte, oob []byte, sa syscall.Sockaddr) (int, int, err
        o := &fd.wop
        o.InitMsg(p, oob)
        if sa != nil {
-               rsa, len, err := sockaddrToRaw(sa)
+               if o.rsa == nil {
+                       o.rsa = new(syscall.RawSockaddrAny)
+               }
+               len, err := sockaddrToRaw(o.rsa, sa)
                if err != nil {
                        return 0, 0, err
                }
-               o.msg.Name = (syscall.Pointer)(rsa)
+               o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
                o.msg.Namelen = len
        }
        n, err := execIO(o, func(o *operation) error {
@@ -1287,8 +1298,11 @@ func (fd *FD) WriteMsgInet4(p []byte, oob []byte, sa *syscall.SockaddrInet4) (in
 
        o := &fd.wop
        o.InitMsg(p, oob)
-       rsa, len := sockaddrInet4ToRaw(sa)
-       o.msg.Name = (syscall.Pointer)(rsa)
+       if o.rsa == nil {
+               o.rsa = new(syscall.RawSockaddrAny)
+       }
+       len := sockaddrInet4ToRaw(o.rsa, sa)
+       o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
        o.msg.Namelen = len
        n, err := execIO(o, func(o *operation) error {
                return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)
@@ -1309,8 +1323,11 @@ func (fd *FD) WriteMsgInet6(p []byte, oob []byte, sa *syscall.SockaddrInet6) (in
 
        o := &fd.wop
        o.InitMsg(p, oob)
-       rsa, len := sockaddrInet6ToRaw(sa)
-       o.msg.Name = (syscall.Pointer)(rsa)
+       if o.rsa == nil {
+               o.rsa = new(syscall.RawSockaddrAny)
+       }
+       len := sockaddrInet6ToRaw(o.rsa, sa)
+       o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
        o.msg.Namelen = len
        n, err := execIO(o, func(o *operation) error {
                return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)