git/list[1] front-page[2] threads[3] people[4] search[5] about
 

Re: [PATCH 4/4] gc docs: downplay the usefulness of --aggressive

From
Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date
Mar 18, 2019, 22:13 UTC
Message-ID
<87k1gvespm.fsf@evledraar.gmail.com>
In-Reply-To
<20190318212227.GD29661@sigill.intra.peff.net>
On Mon, Mar 18 2019, Jeff King wrote:
Show 18 quoted lines
> On Mon, Mar 18, 2019 at 01:28:24PM -0700, Jonathan Nieder wrote:
>
>> > +Using this option may optimize for disk space at the expense of
>> > +runtime performance. See the `--depth` and `--window` documentation in
>> > +linkgit:git-repack[1]. It is not recommended that this option be used
>> > +to improve performance for a given repository without running tailored
>> > +performance benchmarks on it. It may make things better, or worse. Not
>> > +using this at all is the right trade-off for most users and their
>> > +repositories.
>>
>> This part kind of feels like giving up.  Can we make --aggressive have
>> good runtime read performance so we don't have to hedge this way?
>> E.g. is this patch papering over a poor choice of --depth setting in
>> --aggressive?
>
> I thought we already did that, in 07e7dbf0db (gc: default aggressive
> depth to 50, 2016-08-11). As far as I know, "--aggressive" produces
> packs with similar runtime performance.

What happened here is that I'd entirely forgotten about your 07e7dbf0db and in skimming while writing this throught we were still picking larger depth values, which we aren't.

I'll fix that, and see that gc.aggressiveDepth also needs to be changed to note that the depth it's now using as "aggressive" is just the default of 50 you'd get without --aggressive.

Show 5 quoted lines
> It is possible, if it finds more deltas due to the larger window, that
> we'd spend more time accessing those deltas. But if the chains aren't
> long, the base cache tends to perform well, and delta reconstruction is
> about the same cost as zlib inflating. And we have a smaller disk cache
> footprint.

I haven't tested that but suspect it won't matter. We do spend a *lot* more time though, so that still needs to be noted...

On the topic of other things I may have screwed up, is this:
    +The effects of this option are persistent to the extent that
    +`gc.autoPackLimit` and friends don't cause a consolidation of existing
    +pack(s) generated with this option.

Actually wrong since we don't pass -f usually, and thus a one-off --aggressive would live forever for the objects involved in that run no matter if we later consolidate?

From the docs it seems so, but I'd like to confirm...
Previous: Jeff KingNext: Jeff King
Message 16 of 64 in “gc docs: modernize and fix the documentation”
  1. 0/4 gc docs: modernize and fix the documentationÆvar Arnfjörð Bjarmason, Mar 18, 2019
  2. 1/4 gc docs: modernize the advice for manually running "gc"Ævar Arnfjörð Bjarmason, Mar 18, 2019
  3. Jeff KingMar 18, 2019
  4. Ævar Arnfjörð BjarmasonMar 18, 2019
  5. 2/4 gc docs: include the "gc.*" section from "config" in "gc"Ævar Arnfjörð Bjarmason, Mar 18, 2019
  6. Jeff KingMar 18, 2019
  7. Andreas HeidukMar 21, 2019
  8. Duy NguyenMar 19, 2019
  9. 3/4 gc docs: de-duplicate "OPTIONS" and "CONFIGURATION"Ævar Arnfjörð Bjarmason, Mar 18, 2019
  10. Jeff KingMar 18, 2019
  11. Ævar Arnfjörð BjarmasonMar 18, 2019
  12. Jeff KingMar 18, 2019
  13. 4/4 gc docs: downplay the usefulness of --aggressiveÆvar Arnfjörð Bjarmason, Mar 18, 2019
  14. Jonathan NiederMar 18, 2019
  15. Jeff KingMar 18, 2019
  16. Ævar Arnfjörð BjarmasonMar 18, 2019
  17. Jeff KingMar 18, 2019
  18. Johannes SixtMar 19, 2019
  19. Ævar Arnfjörð BjarmasonMar 19, 2019
  20. Jeff KingMar 18, 2019
  21. Ævar Arnfjörð BjarmasonMar 18, 2019
  22. Jeff KingMar 19, 2019
  23. Ævar Arnfjörð BjarmasonMay 6, 2019
  24. Jeff KingMay 7, 2019
  25. Ævar Arnfjörð BjarmasonMay 9, 2019
  26. Jeff KingJul 31, 2019
  27. Ævar Arnfjörð BjarmasonJul 31, 2019
  28. 00/10 gc docs: modernize and fix the documentationÆvar Arnfjörð Bjarmason, Mar 21, 2019
  29. 00/11 gc docs: modernize the advice for manually running "gc"Ævar Arnfjörð Bjarmason, Mar 22, 2019
  30. 01/11 gc docs: modernize the advice for manually running "gc"Ævar Arnfjörð Bjarmason, Mar 22, 2019
  31. 02/11 gc docs: stop noting "repack" flagsÆvar Arnfjörð Bjarmason, Mar 22, 2019
  32. 03/11 gc docs: clean grammar for "gc.bigPackThreshold"Ævar Arnfjörð Bjarmason, Mar 22, 2019
  33. 06/11 gc docs: fix formatting for "gc.writeCommitGraph"Ævar Arnfjörð Bjarmason, Mar 22, 2019
  34. 05/11 gc docs: re-flow the "gc.*" section in "config"Ævar Arnfjörð Bjarmason, Mar 22, 2019
  35. 07/11 gc docs: note how --aggressive impacts --window & --depthÆvar Arnfjörð Bjarmason, Mar 22, 2019
  36. 04/11 gc docs: include the "gc.*" section from "config" in "gc"Ævar Arnfjörð Bjarmason, Mar 22, 2019
  37. Todd ZullingerMar 30, 2019
  38. 00/11 gc docs: modernize and fix the documentationÆvar Arnfjörð Bjarmason, Apr 7, 2019
  39. 01/11 gc docs: modernize the advice for manually running "gc"Ævar Arnfjörð Bjarmason, Apr 7, 2019
  40. 02/11 gc docs: stop noting "repack" flagsÆvar Arnfjörð Bjarmason, Apr 7, 2019
  41. 03/11 gc docs: clean grammar for "gc.bigPackThreshold"Ævar Arnfjörð Bjarmason, Apr 7, 2019
  42. 04/11 gc docs: include the "gc.*" section from "config" in "gc"Ævar Arnfjörð Bjarmason, Apr 7, 2019
  43. 05/11 gc docs: re-flow the "gc.*" section in "config"Ævar Arnfjörð Bjarmason, Apr 7, 2019
  44. 06/11 gc docs: fix formatting for "gc.writeCommitGraph"Ævar Arnfjörð Bjarmason, Apr 7, 2019
  45. 07/11 gc docs: note how --aggressive impacts --window & --depthÆvar Arnfjörð Bjarmason, Apr 7, 2019
  46. 09/11 gc docs: note "gc --aggressive" in "fast-import"Ævar Arnfjörð Bjarmason, Apr 7, 2019
  47. 10/11 gc docs: clarify that "gc" doesn't throw away referenced objectsÆvar Arnfjörð Bjarmason, Apr 7, 2019
  48. 11/11 gc docs: remove incorrect reference to gc.auto=0Ævar Arnfjörð Bjarmason, Apr 7, 2019
  49. 08/11 gc docs: downplay the usefulness of --aggressiveÆvar Arnfjörð Bjarmason, Apr 7, 2019
  50. 10/11 gc docs: clarify that "gc" doesn't throw away referenced objectsÆvar Arnfjörð Bjarmason, Mar 22, 2019
  51. 08/11 gc docs: downplay the usefulness of --aggressiveÆvar Arnfjörð Bjarmason, Mar 22, 2019
  52. 11/11 gc docs: remove incorrect reference to gc.auto=0Ævar Arnfjörð Bjarmason, Mar 22, 2019
  53. 09/11 gc docs: note "gc --aggressive" in "fast-import"Ævar Arnfjörð Bjarmason, Mar 22, 2019
  54. 02/10 gc docs: stop noting "repack" flagsÆvar Arnfjörð Bjarmason, Mar 21, 2019
  55. 01/10 gc docs: modernize the advice for manually running "gc"Ævar Arnfjörð Bjarmason, Mar 21, 2019
  56. Junio C HamanoMar 22, 2019
  57. 03/10 gc docs: clean grammar for "gc.bigPackThreshold"Ævar Arnfjörð Bjarmason, Mar 21, 2019
  58. 04/10 gc docs: include the "gc.*" section from "config" in "gc"Ævar Arnfjörð Bjarmason, Mar 21, 2019
  59. 05/10 gc docs: re-flow the "gc.*" section in "config"Ævar Arnfjörð Bjarmason, Mar 21, 2019
  60. 06/10 gc docs: note how --aggressive impacts --window & --depthÆvar Arnfjörð Bjarmason, Mar 21, 2019
  61. 07/10 gc docs: downplay the usefulness of --aggressiveÆvar Arnfjörð Bjarmason, Mar 21, 2019
  62. 08/10 gc docs: note "gc --aggressive" in "fast-import"Ævar Arnfjörð Bjarmason, Mar 21, 2019
  63. 09/10 gc docs: clarify that "gc" doesn't throw away referenced objectsÆvar Arnfjörð Bjarmason, Mar 21, 2019
  64. 10/10 gc docs: remove incorrect reference to gc.auto=0Ævar Arnfjörð Bjarmason, Mar 21, 2019

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.