[Vortex] PATCH: Send messages in 1kbyte frames

Francis Brosnan Blazquez francis at aspl.es
Thu Apr 24 13:16:34 CEST 2008

Hi Jens,

> Here's the patch I've been talking about: it modifies  
> vortex_sequencer.c to break outgoing messages into 1kbyte frames  
> ("less than 2/3 of the TCP MTU size" as recommended in the RFC.)


> * This improves throughput, especially over high-latency
> connections,  
> by allowing the remote peer to send back a SEQ frame before the
> window  
> fills up, so the sequencer doesn't stall.

Right, this is one issue to solve.

> * It should also make the connection's flow control fairer to all  
> channels, by preventing a channel with large messages from using up  
> most of the bandwidth (a problem that could otherwise get worse if
> the  
> window size is increased.)

Right. Updating the window size is not part of the solution IMHO.

> This patch includes the workaround I mentioned earlier today, i.e.
> it  
> leaves channel 0 alone to avoid breaking up the greetings messages.  
> The standard Vortex regression tests pass, and my application is  
> working reliably (with better throughput than before.)

Ok, let me check your previous reply to get a clear idea. 

In the meantime, here are some data about the performance of the patch
you provided:

With the patch included, a new regression test I'm working on to ensure
performance in all scenarios, shows poor performance [1] under no delay
environments (for example a local area network). However, without the
patch applied [2] better results are found.

In general, the change required to fix the issue you have found (vortex
performance under delay environments) must be dynamic and react properly
under delay and no delay conditions. 


[1] withpath.log
[2] withoutpath.log

Francis Brosnan Blazquez <francis at aspl.es>
Advanced Software Production Line, S.L.
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