Re: [Qemu-devel] [PATCH] ui/vnc: set TCP_NODELAY

[Peter Lieven <pl@kamp.de>]

On 02.09.2014 11:36, Peter Maydell wrote:
> On 2 September 2014 10:21, Peter Lieven <pl@kamp.de> wrote:
>> we currently have the Nagle algorithm enabled for all outgoing VNC updates.
>> This may delay sensitive updates as mouse movements or typing in the console.
>> As we currently prepare all data in a buffer and then send as much as we can
>> this should not cause big trouble. Well established VNC servers like TightVNC
>> set TCP_NODELAY as well.
>> A regular framebuffer update request generates exactly one framebuffer update
>> which should be pushed out as fast as possible.
>>
>> Signed-off-by: Peter Lieven <pl@kamp.de>
>> ---
>>   ui/vnc.c |    4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/ui/vnc.c b/ui/vnc.c
>> index 1bc1ae0..b12d0ea 100644
>> --- a/ui/vnc.c
>> +++ b/ui/vnc.c
>> @@ -2885,6 +2885,10 @@ static void vnc_listen_read(void *opaque, bool websocket)
>>       }
>>
>>       if (csock != -1) {
>> +#ifdef TCP_NODELAY
>> +        int flag = 1;
>> +        setsockopt(csock, IPPROTO_TCP, TCP_NODELAY, (char *) &flag, sizeof(int));
>> +#endif
>>           vnc_connect(vs, csock, false, websocket);
> Why not just call socket_set_nodelay() ?

I was not aware of that helper function. Thanks for the pointer.

Peter

>
> thanks
> -- PMM