Re: [Haskell-cafe] Re: announcing darcs 2.0.0pre2
On Mon, Dec 17, 2007 at 12:29:20PM +, Simon Marlow wrote: David Roundy wrote: I am pleased to announce the availability of the second prerelease of darcs two, darcs 2.0.0pre2. Thanks! Continuing my performance tests, I tried unpulling and re-pulling a bunch of patches in a GHC tree. I'm unpulling about 400 patches using --from-tag, and then pulling them again from a local repo. Summary: darcs2 is about 10x slower than darcs1 on unpull, and on pull it is 100x slower in user time but only 20x slower in elapsed time. I'm not seeing this behavior right now, but am unsure whether it's because of something in my testing, or if I've improved something. I definitely fixed a problem in the no-patches-to-pull case, where we were unnecessarily reading the entire repository because of inadequate laziness. Another possibility is that the problem is one that shows up because of the way the repositories were generated. Incidentally, I *think* that with the latest convert, optimize should be a noop, and if it's not, I'd be interested to hear (but haven't gotten around to testing...). I suspect that if you perform the same sequence in the reverse direction (unpull and repull, but running the commands in the other repository), then you'll see much better performance. My suspicion is that the trouble is that optimize only optimizes for changes since the last tag, so by unpulling this many patches you're going back into unoptimized territory. I'm toying with making optimize do a deep optimize, but then it'll always be O(N^2), which is a little scary. On the other hand, since we now auto-optimize, making the real thing more expensive shouldn't hurt as much (since it'll not be needed very often). Anyhow, could you retry this test with the above change in methodology, and let me know if (a) the pull is still slow the first time and (b) if it's much faster the second time (after the reverse unpull/pull)? Thanks! David (who is doing darcs hacking in the morning, before the other grownups wake up) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: announcing darcs 2.0.0pre2
Thanks for the timings. Alas, I'm leaving in the morning for vacation, so I'm not sure when I'll have time to profile these operations. And I'm still puzzling over how to speed up darcs get (i.e. the long discussion of http pipelining, which will not, of course, do anything to help the poor folks stuck with ssh...). The 100x slower pull is indeed a bit puzzling. I can't help but wonder if it's the hash-checking (but that seems very unlikely)... David On Mon, Dec 17, 2007 at 12:29:20PM +, Simon Marlow wrote: Continuing my performance tests, I tried unpulling and re-pulling a bunch of patches in a GHC tree. I'm unpulling about 400 patches using --from-tag, and then pulling them again from a local repo. Summary: darcs2 is about 10x slower than darcs1 on unpull, and on pull it is 100x slower in user time but only 20x slower in elapsed time. In both cases, the repository was on an NFS filesystem. In the darcs2 case, the repository I was pulling from was on the local disk, and I'm also using a cache (NFS-mounted). The darcs2 repository has been optimized, but the darcs1 repository has not (at lesat, not recently). I did all of these a couple of times to eliminate the effects of cache preloading etc., the times reported are from the second run. --- darcs 1: $ time darcs unpull --from-tag 2007-09-25 -a Finished unpulling. 35.17s real 5.77s user 1.00s system 19% darcs unpull --from-tag 2007-09-25 -a $ time darcs pull ~/ghc-HEAD -a Pulling from /home/simonmar/ghc-HEAD... 33.51s real 3.62s user 1.05s system 13% darcs pull ~/ghc-HEAD -a --- darcs 2: $ time darcs2 unpull --from-tag 2007-09-25 -a Finished unpulling. 385.22s real 52.18s user 12.62s system 16% darcs2 unpull --from-tag 2007-09-25 -a $ time darcs2 pull /64playpen/simonmar/ghc-darcs2 -a Finished pulling and applying. 668.75s real 290.74s user 15.03s system 45% darcs2 pull /64playpen/simonmar/ghc-darcs2 -a -- David Roundy Department of Physics Oregon State University ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
