[tor-bugs] #12889 [general]: Simulate global circuit scheduling from #9262

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#12889: Simulate global circuit scheduling from #9262
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     Reporter:  robgjansen  |      Owner:  robgjansen
         Type:  task        |     Status:  new
     Priority:  normal      |  Milestone:
    Component:  general     |    Version:
   Resolution:              |   Keywords:  Shadow
Actual Points:              |  Parent ID:  #12541
       Points:              |
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Comment (by robgjansen):

 I simulated vanilla Tor 0.2.5.6-alpha as well as Roger's cmux-0256 branch
 using Shadow. I assume that the new global circuit scheduling approach is
 enabled by default in the cmux branch since I didn't notice any new config
 options related to it.

 I'm not exactly sure how to validate that cmux is working correctly. I
 drew the performance graphs I typically use to understand how things are
 working at a high level. The results are attached
 [https://trac.torproject.org/projects/tor/attachment/ticket/12889
 /shadowtor-400r-perf1.pdf here] and
 [https://trac.torproject.org/projects/tor/attachment/ticket/12889
 /shadowtor-400r-perf2.pdf here]. (The two sets of graphs are drawn on the
 same data.)

 If working correctly, then the EWMA circuit scheduler should be doing a
 better job of de-prioritizing circuits as more and more bytes flow through
 it. The graphs seem to indicate that global scheduling improves latency
 (first byte), but most total download times have gotten a bit worse. As a
 result of Shadow's client model, longer web download times means fewer web
 downloads will complete over the entire simulation. The graphs also show
 this.

 I think more data analysis is a good idea to assert correctness and
 determine how global scheduling affects circuit EWMA values and
 throughput. I am requesting feedback about how to do that, and especially
 about how to push this task forward.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12889#comment:1>
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