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Re: remove_duplicates() in builtin/fetch-pack.c is O(N^2)

From
Jeff King <peff@peff.net>
Date
May 22, 2012, 07:37 UTC
Message-ID
<20120522073740.GA10093@sigill.intra.peff.net>
In-Reply-To
<4FBB3D2B.4010300@alum.mit.edu>
On Tue, May 22, 2012 at 09:15:55AM +0200, Michael Haggerty wrote:
Show 5 quoted lines
> If it is not too much trouble, please let me know where I can obtain
> your test repo and what commands you used to get your result.  (Was
> the local repo already a full clone of the remote, including all 400k
> references?  How was the remote set up--sharing data or not, local or
> remote?  Warm or cold disk cache?)
I've put the repo up at:
  https://gist.github.com/raw/2767328/603926240fabb4d3e3abc3c93a1913d91852cc7e/rails.tar.gz
You can reproduce the slow-down with:
  cd rails.git &&
  git fetch . refs/*:refs/*

which should be a no-op, as we already have all of the refs. I don't know if the problem is actually specific to fetch; that was just how I noticed it.

When I try it with both 'next' and v1.7.10, I see that the latter is much faster. I did my tests with a warm cache, but the interesting number is the CPU time, which is quite different.

-Peff
Previous: Michael HaggertyNext: Michael Haggerty
Message 20 of 46 in “remove_duplicates() in builtin/fetch-pack.c is O(N^2)”
  1. Michael HaggertyMay 21, 2012
  2. Junio C HamanoMay 21, 2012
  3. demerphqMay 21, 2012
  4. Jeff KingMay 21, 2012
  5. Jeff KingMay 21, 2012
  6. 1/5 fetch-pack: sort incoming headsJeff King, May 21, 2012
  7. Junio C HamanoMay 22, 2012
  8. Jeff KingMay 22, 2012
  9. Jeff KingMay 24, 2012
  10. 2/5 fetch-pack: avoid quadratic behavior in remove_duplicatesJeff King, May 21, 2012
  11. 3/5 add sorting infrastructure for list refsJeff King, May 21, 2012
  12. 4/5 fetch-pack: sort the list of incoming refsJeff King, May 21, 2012
  13. 5/5 fetch-pack: avoid quadratic loop in filter_refsJeff King, May 21, 2012
  14. Junio C HamanoMay 22, 2012
  15. Jeff KingMay 21, 2012
  16. Jeff KingMay 22, 2012
  17. Michael HaggertyMay 22, 2012
  18. Jeff KingMay 22, 2012
  19. Michael HaggertyMay 22, 2012
  20. Jeff KingMay 22, 2012
  21. Michael HaggertyMay 22, 2012
  22. Jeff KingMay 22, 2012
  23. Michael HaggertyMay 24, 2012
  24. Martin FickMay 25, 2012
  25. Jeff KingMay 25, 2012
  26. Martin FickMay 25, 2012
  27. Jeff KingMay 25, 2012
  28. Martin FickMay 25, 2012
  29. Jeff KingMay 25, 2012
  30. Nguyen Thai Ngoc DuyMay 22, 2012
  31. Michael HaggertyMay 22, 2012
  32. Jeff KingMay 22, 2012
  33. Junio C HamanoMay 22, 2012
  34. Jeff KingMay 22, 2012
  35. Michael HaggertyMay 24, 2012
  36. Nguyen Thai Ngoc DuyMay 23, 2012
  37. Junio C HamanoMay 22, 2012
  38. Martin FickMay 21, 2012
  39. Jeff KingMay 21, 2012
  40. Junio C HamanoMay 21, 2012
  41. Jeff KingMay 21, 2012
  42. Martin FickMay 22, 2012
  43. Jeff KingMay 22, 2012
  44. Martin FickMay 22, 2012
  45. Junio C HamanoMay 22, 2012
  46. Martin FickMay 23, 2012

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