Re: [Qemu-devel] [PATCH] net: use socket_set_nodelay() for -netdev socket

[Daniel P. Berrange]

On Wed, Feb 27, 2013 at 03:05:47PM +0100, Stefan Hajnoczi wrote:
> Reduce -netdev socket latency by disabling the Nagle algorithm on
> SOCK_STREAM sockets in net/socket.c.  Since we are tunelling Ethernet
> over TCP we shouldn't artificially delay outgoing packets, let the guest
> decide packet scheduling.
> 
> I already get sub-millisecond -netdev socket ping times on localhost, so
> there was no measurable difference in my testing.  This won't hurt
> though and may improve remote socket performance.
> 
> Signed-off-by: Stefan Hajnoczi <address@hidden>

ACK.

Signed-off-by: Daniel P. Berrange <address@hidden>

> ---
>  net/socket.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/socket.c b/net/socket.c
> index 396dc8c..c0dcc31 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -439,6 +439,9 @@ static NetSocketState 
> *net_socket_fd_init_stream(NetClientState *peer,
>      s->fd = fd;
>      s->listen_fd = -1;
>  
> +    /* Disable Nagle algorithm on TCP sockets to reduce latency */
> +    socket_set_nodelay(fd);
> +
>      if (is_connected) {
>          net_socket_connect(s);
>      } else {
> -- 


Daniel
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