[darcs-users] report on using darcs- (performance of "darcs query contents")

Zooko Wilcox-O'Hearn zooko at zooko.com
Sat Jul 11 20:22:54 UTC 2009


I tried out darcs- (upgrading from darcs-2.2.0).  Everything  
that I tried works fine, but the performance of "darcs query  
contents" (http://bugs.darcs.net/issue1477 ) is not better.  In fact,  
it seems to be slightly worse.

For darcs- compiled with ghc-6.10.3, the best run out of nine  
runs of:

darcs query contents --quiet --match "hash  

was 3.13s and the worst was 3.48s (all measurements are user CPU time  
reported by "time").

For darcs-2.2.0 compiled with ghc-6.10.1 the best was 2.98s and the  
worst was 3.19s.

I started to wonder if part of it was a performance regression from  
ghc-6.10.1 to ghc-6.10.3 so I recompiled darcs-2.2.0 with ghc-6.10.3  
and got: best 3.21s, worst: 4.11s.  Huh.  So, unless my benchmarks  
were perturbed by shifting load on this server, it almost looks like  
darcs- improves performance over darcs-2.2.0, but ghc-6.10.3  
reduces performance over ghc-6.10.1.  In order to experiment further,  
I compiled darcs- with ghc-6.10.1:

best: 3.05s, worst: 3.29s

Oh well, I guess it's just random variation in my benchmarks.  Just  
to double-check, I ran nine more measurements with darcs-2.2.0  
compiled with ghc-6.10.1: best: 3.01s, worst: 3.25s.

Of course, this hardly matters anyway to my tracdarcs use case; what  
I really need for tracdarcs is for "darcs query contents" to return  
the same answers in about 1/100 of the time it currently takes (i.e.  
about 30 milliseconds would be an improvement), or perhaps to allow  
queries on multiple files in a single call so that the tracdarcs  
plugin doesn't need to invoke it dozens of times in order to render a  
directory full of dozens of files.  See http://bugs.darcs.net/ 
issue1477 for details.



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