You cannot, the address of sa escapes to the heap because it is returned to
the caller. The solution may be to refactor the method to take a
*syscall.SockaddrInet4 that was allocated in the caller, but that is not
something that can be done as a consumer of the net package.
On Tuesday, 2 August 2016 18:21:35 UTC+10, Михаил Монашёв wrote:
>
> Hi, golang-nuts.
>
> I'm trying to speed up my app, and deleted all of memory allocation
> from my code. But how to prevent memory allocation here?
>
>
> ROUTINE ======================== net.ipToSockaddr in
> C:/Go/src/net/ipsock_posix.go
> 516093 516093 (flat, cum) 24.33% of Total
> . . 166: }
> . . 167: ip4 := ip.To4()
> . . 168: if ip4 == nil {
> . . 169: return nil,
> &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
> . . 170: }
> 516093 516093 171: sa := &syscall.SockaddrInet4{Port:
> port}
> . . 172: copy(sa.Addr[:], ip4)
> . . 173: return sa, nil
> . . 174: case syscall.AF_INET6:
> . . 175: // In general, an IP wildcard
> address, which is either
> . . 176: // "0.0.0.0" or "::", means the
> entire IP addressing
> ROUTINE ======================== syscall.(*RawSockaddrAny).Sockaddr in
> C:/Go/src/syscall/syscall_windows.go
> 516158 516158 (flat, cum) 24.33% of Total
> . . 678: case AF_UNIX:
> . . 679: return nil, EWINDOWS
> . . 680:
> . . 681: case AF_INET:
> . . 682: pp :=
> (*RawSockaddrInet4)(unsafe.Pointer(rsa))
> 516158 516158 683: sa := new(SockaddrInet4)
> . . 684: p :=
> (*[2]byte)(unsafe.Pointer(&pp.Port))
> . . 685: sa.Port = int(p[0])<<8 + int(p[1])
> . . 686: for i := 0; i < len(sa.Addr); i++
> {
> . . 687: sa.Addr[i] = pp.Addr[i]
> . . 688: }
> ROUTINE ======================== net.(*UDPConn).readFrom in
> C:/Go/src/net/udpsock_posix.go
> 516028 1168218 (flat, cum) 55.07% of Total
> . . 38: return ipToSockaddr(family, a.IP, a.Port,
> a.Zone)
> . . 39:}
> . . 40:
> . . 41:func (c *UDPConn) readFrom(b []byte) (int,
> *UDPAddr, error) {
> . . 42: var addr *UDPAddr
> . 652190 43: n, sa, err := c.fd.readFrom(b)
> . . 44: switch sa := sa.(type) {
> . . 45: case *syscall.SockaddrInet4:
> 516028 516028 46: addr = &UDPAddr{IP: sa.Addr[0:],
> Port: sa.Port}
> . . 47: case *syscall.SockaddrInet6:
> . . 48: addr = &UDPAddr{IP: sa.Addr[0:],
> Port: sa.Port, Zone: zoneToString(int(sa.ZoneId))}
> . . 49: }
> . . 50: return n, addr, err
> . . 51:}
> Total: 2121170
> ROUTINE ======================== syscall.WSARecv in
> C:/Go/src/syscall/zsyscall_windows.go
> 122693 122695 (flat, cum) 5.78% of Total
> . . 1515: Syscall9(procGetAcceptExSockaddrs.Addr(),
> 8, uintptr(unsafe.Pointer(buf)), uintptr(rxdatalen),
> uintptr(laddrlen), uintptr(raddrlen), uintptr(unsafe.Pointer(lrsa)),
> uintptr(unsafe.Pointer(lrsalen)), uintptr(unsafe.Pointer
> (rrsa)), uintptr(unsafe.Pointer(rrsalen)), 0)
> . . 1516: return
> . . 1517:}
> . . 1518:
> . . 1519:func WSARecv(s Handle, bufs *WSABuf, bufcnt
> uint32, recvd *uint32, flags *uint32, overlapped *Ove
> rlapped, croutine *byte) (err error) {
> . 2 1520: r1, _, e1 := Syscall9(procWSARecv.Addr(),
> 7, uintptr(s), uintptr(unsafe.Pointer(bufs)), uintpt
> r(bufcnt), uintptr(unsafe.Pointer(recvd)), uintptr(unsafe.Pointer(flags)),
> uintptr(unsafe.Pointer(overlapped)), uintptr(unsafe
> .Pointer(croutine)), 0, 0)
> . . 1521: if r1 == socket_error {
> . . 1522: if e1 != 0 {
> 122693 122693 1523: err = error(e1)
> . . 1524: } else {
> . . 1525: err = EINVAL
> . . 1526: }
> . . 1527: }
> . . 1528: return
> ROUTINE ======================== syscall.WSARecvFrom in
> C:/Go/src/syscall/zsyscall_windows.go
> 135757 135757 (flat, cum) 6.40% of Total
> . . 1542:
> . . 1543:func WSARecvFrom(s Handle, bufs *WSABuf,
> bufcnt uint32, recvd *uint32, flags *uint32, from *RawSo
> ckaddrAny, fromlen *int32, overlapped *Overlapped, croutine *byte) (err
> error) {
> . . 1544: r1, _, e1 :=
> Syscall9(procWSARecvFrom.Addr(), 9, uintptr(s),
> uintptr(unsafe.Pointer(bufs)), ui
> ntptr(bufcnt), uintptr(unsafe.Pointer(recvd)),
> uintptr(unsafe.Pointer(flags)), uintptr(unsafe.Pointer(from)),
> uintptr(unsafe.P
> ointer(fromlen)), uintptr(unsafe.Pointer(overlapped)),
> uintptr(unsafe.Pointer(croutine)))
> . . 1545: if r1 == socket_error {
> . . 1546: if e1 != 0 {
> 135757 135757 1547: err = error(e1)
> . . 1548: } else {
> . . 1549: err = EINVAL
> . . 1550: }
> . . 1551: }
> . . 1552: return
>
>
> --
>
> Michael
>
>
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