New passive performance metrics in Tor

Robert Hogan robert at
Mon Aug 16 18:09:13 UTC 2010

On Monday 12 July 2010 12:17:47 Karsten Loesing wrote:
> Hi everyone,
> I'm planning to add new passive performance metrics to Tor so that we
> can better understand why it's slow and how we can improve it. Here is a
> list of performance metrics we already have and a few ideas for new
> metrics. If anyone has an idea what other metrics might be missing or
> how we can improve the existing/planned metrics, please let us know!
Hi Karsten,

Hope I'm not too late.  This is connected to:

It would be useful to know how many cells relays are sending to streams 
after they have received a RELAY_END on the stream from the client.

On a poor-performing circuit terminating at a fast exit, a RELAY_END on a 
stream can result in up to 1000 queued cells getting flushed to a client 
that doesn't want them anymore. This wastage of bandwidth can't be remedied 
without just tearing down the circuit or resetting it in some way.

This metric would tell us how much of this wasted bandwidth there is on the 
network and whether it merits action.

I can implement for your review if you are amenable to the idea.


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