[tahoe-lafs-trac-stream] [tahoe-lafs] #1180: put more DYHBs into flight at once when K is larger

tahoe-lafs trac at tahoe-lafs.org
Mon Apr 11 10:01:59 PDT 2011


#1180: put more DYHBs into flight at once when K is larger
-------------------------+-------------------------------------------------
     Reporter:  zooko    |      Owner:
         Type:  defect   |     Status:  new
     Priority:  major    |  Milestone:  soon
    Component:  code-    |    Version:  1.8β
  network                |   Keywords:  easy immutable download performance
   Resolution:           |  regression
Launchpad Bug:           |
-------------------------+-------------------------------------------------
Description changed by zooko:

Old description:

> As mentioned in comment:8:ticket:448, the new downloader code in v1.8.0
> will put at most 10 DYHBs into flight at once. This is perfect when
> {{{K=3}}}, but as {{{K}}} gets larger it is increasingly likely that the
> hardcoded limit of {{{10}}} will induce delay at the beginning of a
> download or cause the downloader to overlook a better-performing server.
> As Brian suggested on #448, a better limit would be something like {{{K *
> 3}}}.
>
> (Note: everyone that I know of uses the default settings of {{{K=3,
> M=10}}}. The theoretical maximum value of {{{K}}} is 256. I think there
> might be other problems with using {{{K}}} greater than about {{{100}}},
> such as a worse rate of a storage server failing during your download,
> but I'm not sure.)

New description:

 As mentioned in comment:8:ticket:448, the new downloader code in v1.8.0
 will put at most 10 DYHBs into flight at once. This is perfect when
 {{{K=3}}}, but as {{{K}}} gets larger it is increasingly likely that the
 hardcoded limit of {{{10}}} will induce delay at the beginning of a
 download or cause the downloader to overlook a better-performing server.
 As Brian suggested on #448, a better limit would be something like {{{K *
 3}}}.

 (Note: everyone that I know of uses the default settings of {{{K=3,
 M=10}}}. The theoretical maximum value of {{{K}}} is 256. Since nobody has
 tried it, we don't know if there are other problems with using {{{K}}}
 greater than about {{{100}}}.)

--

-- 
Ticket URL: <http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1180#comment:4>
tahoe-lafs <http://tahoe-lafs.org>
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