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Re: [PATCH v2 0/9] address packed-refs speed regressions

From
Jeff King <peff@peff.net>
Date
Apr 16, 2015, 09:25 UTC
Message-ID
<20150416092518.GA18135@peff.net>
In-Reply-To
<20150416084733.GA17811@peff.net>
On Thu, Apr 16, 2015 at 04:47:34AM -0400, Jeff King wrote:
Show 10 quoted lines
> Here's a re-roll incorporating feedback from the list. Thanks everybody
> for your comments. Last time the final number was ~8.5s, which was
> disappointingly slower than v2.0.0. In this iteration, my final numbers
> are:
> 
>   real    0m5.703s
>   user    0m5.276s
>   sys     0m0.432s
> 
> which is quite pleasing.
I forgot to mention what I _didn't_ include.

We discussed using mmap instead of stdio. Applying René's mmap patch drops my best-of-five here to 5.114s. Which is nice, but it is a bit more invasive (and does not help other callers of strbuf_getline).

If I further apply my really nasty patch to avoid the strbuf entirely (i.e., we parse straight out of the mmap), I can get it down to 4.835s.

I don't know if the complexity is worth it or not. Ultimately, I think the best route to making packed-refs faster is to drop the whole ref_cache structure and just iterate directly over the mmap data. It would use less RAM, and it opens the possibility of binary-searching to look at only a subset of the entries. That's a _lot_ more invasive, though.

-Peff
Previous: Jeff King
Message 44 of 44 in “address packed-refs speed regressions”
  1. 0/6 address packed-refs speed regressionsJeff King, Apr 5, 2015
  2. 1/6 strbuf_getwholeline: use getc macroJeff King, Apr 5, 2015
  3. 2/6 git-compat-util: add fallbacks for unlocked stdioJeff King, Apr 5, 2015
  4. 3/6 strbuf_getwholeline: use getc_unlockedJeff King, Apr 5, 2015
  5. Jeff KingApr 5, 2015
  6. Jeff KingApr 5, 2015
  7. Jeff KingApr 5, 2015
  8. Junio C HamanoApr 5, 2015
  9. Duy NguyenApr 5, 2015
  10. Jeff KingApr 5, 2015
  11. Junio C HamanoApr 5, 2015
  12. Rasmus VillemoesApr 7, 2015
  13. Jeff KingApr 7, 2015
  14. Rasmus VillemoesApr 7, 2015
  15. Jeff KingApr 8, 2015
  16. 4/6 strbuf: add an optimized 1-character strbuf_growJeff King, Apr 5, 2015
  17. Eric SunshineApr 6, 2015
  18. Jeff KingApr 6, 2015
  19. 5/6 t1430: add another refs-escape testJeff King, Apr 5, 2015
  20. 6/6 refname_is_safe: avoid expensive normalize_path_copy callJeff King, Apr 5, 2015
  21. René ScharfeApr 5, 2015
  22. Jeff KingApr 5, 2015
  23. Jeff KingApr 5, 2015
  24. René ScharfeApr 5, 2015
  25. René ScharfeApr 5, 2015
  26. Jeff KingApr 6, 2015
  27. 0/9 address packed-refs speed regressionsJeff King, Apr 16, 2015
  28. 1/9 strbuf_getwholeline: use getc macroJeff King, Apr 16, 2015
  29. 2/9 git-compat-util: add fallbacks for unlocked stdioJeff King, Apr 16, 2015
  30. 3/9 strbuf_getwholeline: use getc_unlockedJeff King, Apr 16, 2015
  31. 4/9 config: use getc_unlocked when reading from fileJeff King, Apr 16, 2015
  32. 5/9 strbuf_addch: avoid calling strbuf_growJeff King, Apr 16, 2015
  33. 6/9 strbuf_getwholeline: avoid calling strbuf_growJeff King, Apr 16, 2015
  34. 7/9 strbuf_getwholeline: use getdelim if it is availableJeff King, Apr 16, 2015
  35. Eric SunshineApr 17, 2015
  36. Jeff KingApr 21, 2015
  37. Eric SunshineMay 8, 2015
  38. Jeff KingMay 9, 2015
  39. Eric SunshineJun 2, 2015
  40. Johannes SchindelinApr 22, 2015
  41. Jeff KingApr 22, 2015
  42. 8/9 read_packed_refs: avoid double-checking sane refsJeff King, Apr 16, 2015
  43. 9/9 t1430: add another refs-escape testJeff King, Apr 16, 2015
  44. Jeff KingApr 16, 2015

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