[tor-bugs] #25716 [Core Tor/Tor]: Arrange an experiment on the test network where we dump create cells on a relay and time the responses

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#25716: Arrange an experiment on the test network where we dump create cells on a
relay and time the responses
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     Reporter:  arma          |      Owner:  (none)
         Type:  task          |     Status:  new
     Priority:  Medium        |  Milestone:
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 In #25347 I asked: "Do we have any reason to believe that the calculation
 in have_room_for_onionskin() is at all accurate? That is, are we sometimes
 sending this response when there are only 0.25 seconds worth of create
 cells in our queue? Or are we sometimes not sending them even though there
 are 5 seconds of cells queued?"

 We have a test network, with real relays on it.

 We should arrange an experiment where we fill a relay with various levels
 of create cell load, and keep track of response times and response codes.
 For one, that will help us tune the calculation that
 have_room_for_onionskin() makes. For two, it will help us with a new level
 of testing that we don't get from our unit tests.

 Ideally we should arrange the experiment so it is easy to repeat, and then
 we can run it periodically (as a regression test) without too much
 additional effort. And e.g. run it with the relay using various values of
 NumCPUs.

 In particular, I am interested to discover if we waste a lot of time in
 the "glue" stages of the cpuworker where we could be more efficient about
 queueing work items well but we're not. And, as we get better with
 modularization, we should be able to see an improvement here.

 See #7291 for where this timing estimation thing first came in.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25716>
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