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doubts about MDMF download "linear in k" slowdown 

[Imported from Trac: page Performance/Sep2011, version 5]
warner 2012-05-20 18:03:59 +00:00
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24
Performance/Sep2011.md

@ -94,3 +94,27 @@ Some graphs were added to
Complete benchmark toolchain and data included in
[atlasperf.git.tar.gz](../raw/attachments/Performance/Sep2011/atlasperf.git.tar.gz)
Zooko raised the question (20-May-2012) on IRC:
```
<zooko> warner: this page says that K=60 takes twice as long as K=30:
<zooko> https://tahoe-lafs.org/trac/tahoe-lafs/wiki/Performance/Sep2011
<zooko> But these graphs seems to show those two taking about the same time as
each other:
<zooko>
https://tahoe-lafs.org/trac/tahoe-lafs/attachment/wiki/Performance/Sep2011/MDMF-100MB-partial.png
<zooko>
https://tahoe-lafs.org/trac/tahoe-lafs/attachment/wiki/Performance/Sep2011/MDMF-1MB-partial.png
<zooko> I hope the latter is true. :-)
```
Those partial-read graphs certainly don't show a linear difference
between k=30 and k=60. At best there might be a 4% difference between
k=3 and k=30, and k=30/k=60 look identical.
I think I was prompted to write that sentence by looking at the yellow
"trunk-MDMF" line in the [CHKMDMF-100MB-vs-k.png](../raw/attachments/Performance/Sep2011/CHKMDMF-100MB-vs-k.png) graph, which
*does* show a linear slowdown with increasing k (with a lower multiplier
than the new-immutable-downloader). I don't know how to reconcile the
two. So something is funny, and I need to review the data, and possible
run new tests.