[tor-bugs] #20459 [Core Tor/Tor]: ewma_cmp_cmux never considers policies different

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#20459: ewma_cmp_cmux never considers policies different
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 Reporter:  pastly                         |          Owner:
     Type:  defect                         |         Status:  closed
 Priority:  High                           |      Milestone:  Tor:
                                           |  0.3.0.x-final
Component:  Core Tor/Tor                   |        Version:  Tor:
                                           |  0.2.6.2-alpha
 Severity:  Normal                         |     Resolution:  fixed
 Keywords:  029-backport, review-group-11  |  Actual Points:
Parent ID:                                 |         Points:
 Reviewer:                                 |        Sponsor:
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Comment (by pastly):

 Ready for some graphs? This data was collected from two shadow
 simulations. Each has 500 relays and 7500 clients. The one line summary of
 the results (to me) is: the ewma fix does no harm by the metrics I
 gathered.

 qtime.shadow.results.pdf shows the amount of time a cell spends in the
 kernel outbound buffer after leaving Tor and becoming bytes. As you can
 see, no change.

 shadow.results.pdf shows a lot.

 - Time to download `x` bytes are for each different type of client.
 Clients with a smaller `x` behave a lot like web browsers. Clients with
 larger `x` are near continuous bulk downloads. Looks like no change.
 - A bunch of probably self-explanatory graphs all showing no change.
 - 60 second moving average read (pg 22) and write (pg 25). We give the
 network 30 simulation minutes for every relay/client to boot up and reach
 steady state, then measure for 10 simulation minutes. 'After' seems more
 stable than 'before', which would explain the better read and write
 performance for 'after'.

 So, IMO, the fix causes no harm and is beneficial. I can answer any
 questions about what graphs mean, what the simulations consist of, etc.

 I will attach the files right after hitting submit on this. Because I
 can't do it all at once ... ?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20459#comment:14>
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