[tor-bugs] #34171 [Core Tor/Tor]: possible single circuit maximum transfer rate regression in 0.3.4

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#34171: possible single circuit maximum transfer rate regression in 0.3.4
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 Reporter:  starlight     |          Owner:  (none)
     Type:  defect        |         Status:  needs_information
 Priority:  Medium        |      Milestone:
Component:  Core Tor/Tor  |        Version:  Tor: 0.3.4.10
 Severity:  Normal        |     Resolution:
 Keywords:                |  Actual Points:
Parent ID:                |         Points:
 Reviewer:                |        Sponsor:
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Comment (by starlight):

 I have a relay running vanilla scheduler (disabled KIST everywhere when I
 noticed #29427 around the time it appeared) where the transfer rate maxes
 at 2 mbyte per second now--even when when traffic is light and right after
 a restart.  Just noticed this; two years ago it could easily manage 5
 mbyte/sec for a single connection even under moderately high load.  Direct
 'curl' downloads of same files on the system where the relay runs hit
 sustained 24 mbyte/sec.

 Have logged bandwidth scanner votes for over two years and observe a sharp
 and permanent Torflow ratio drop in Decemmber 2018.  The system runs in
 the central European Internet, has CDN grade connectivity.

 Plan on investigating further by running old versions of tor in no-
 publish-descriptor mode and repeating the experiments, but it's an
 important issue and I opened the ticket after becoming convinced the
 problem is real rather than waiting.  If it proves out, this has
 implications for the state of bandwidth measurements and load balancing in
 the network.

 In #29427 KIST related transfer rate impairment shown in the graph is
 huge.  I am doubtful regarding the cost vs benefit of the feature.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/34171#comment:3>
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