[Spice-devel] [PATCH v2 spice-protocol 2/2] Add qos related messages

[Yonit Halperin]

On 04/18/2012 08:47 PM, Marc-André Lureau wrote:
> Hi
>
> On Wed, Apr 18, 2012 at 7:34 PM, Marc-André Lureau
> <marcandre.lureau at gmail.com>  wrote:
>> It would be
>> ->  QOS_QUERY(nbytes)
>> ->  nbytes of various messages 1 or n
>> <- QOS_ACK
>
> Further questions about this, how can the server really determine the
> bandwidth? (I suppose this is the goal)
>
> There might be data queued on the upstream link, and then latency and
> other factors are affecting the result.
>
The latency factor is in my TODO (see cover letter).
I use ioctl(socket, TIOCOUTQ) in order to find how many bytes are 
pending in the tcp snd buffer, in addition to the size of the message.
So I calculate the bandwidth by (message_size + ioctl(socket, 
TIOCOUTQ))/ack_time.
When I add the latency, it will be (message_size + ioctl(socket, 
TIOCOUTQ)) / (ack_time - latency)

This measurement can be affected by other links, but I think it is what 
we want -> the actual bandwidth available for the channel.

> It could perhaps be more reliable if the messages would be:
>
> ->  QOS_QUERY(nbytes)
> ->  nbytes of various messages data
> <- QOS_ACK(N Bps)
>
>
> Btw, those messages should be symmetric, so we could measure
> upload/download (it's always fun to reinvent the wheel!
>
Currently all the channels are mainly asymmetric (maybe except for the 
usb). Specifically, for the display channel, which is currently the only 
consumer of bandwidth data, the upload statistics are the most important 
ones. In the future we may want to implement it in the client side as 
well (for record channel, and usb), and add the symmetric messages.

Yonit.