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Re: [PATCH v4 07/14] bloom: split 'get_bloom_filter()' in two

From
Taylor Blau <me@ttaylorr.com>
Date
Sep 5, 2020, 18:01 UTC
Message-ID
<20200905180120.GB6820@nand.local>
In-Reply-To
<CANQwDwcWveN03h=Ex0GFo-Mm89UT8_HXFMQcZWdDx9MPZYYodQ@mail.gmail.com>
On Sat, Sep 05, 2020 at 07:50:01PM +0200, Jakub Narębski wrote:
Show 12 quoted lines
> Hello,
>
> On Sat, 5 Sep 2020 at 19:38, Taylor Blau <me@ttaylorr.com> wrote:
> > Right, once we get handed back a filter from
> > 'get_or_compute_bloom_filter()', we can't distinguish between (a) a
> > commit with too many changes to store in a single Bloom filter, and (b)
> > a commit with no changes at all.
>
> We could change how we store either no-changes Bloom filter (as all
> zeros minimal size filter), or too-many-changes Bloom filter (as all
> ones, i.e. max unsigned value, minimal size filter). This change would
> not require to change any user of Bloom filter.

I don't think that's true. Say that we changed the empty Bloom filter to be encoded as only having the most-significant bit set. First, we'd have to write a Bloom filter where we didn't have to before. But the real issue is that commit-graph files generated with new clients would suddenly be unreadable by old clients.

Show 11 quoted lines
>
> > It's unfortunate that callers can't pick between the two, but this
> > implementation is actually an improvement on the status-quo! Why?
> > Because right now we'll see an "empty" Bloom filter and recompute it
> > because it's "missing", only to discover that it has no changes.
> >
> > With this patch, we'll say "this filter looks too large", and stop
> > computing it, because we have already gone through the effort to compute
> > it once (and marked it in the BFXL chunk).
>
> Can we use this when computing trace2 values?

We could, but I don't think it's absolutely necessary. The test coverage in t4216 gives us enough confidence already.

Show 7 quoted lines
> [...]
> > > This is a minor issue, though.
> >
> > Thanks for raising it. I don't think that this is a show-stopper for
> > this series.
>
> I agree.
Thanks for your input!
> Best,
> --
> Jakub Narębski

Thanks, Taylor

Previous: Jakub NarębskiNext: Jakub Narębski
Message 100 of 117 in “more miscellaneous Bloom filter improvements”
  1. 00/10 more miscellaneous Bloom filter improvementsTaylor Blau, Aug 3, 2020
  2. 01/10 commit-graph: introduce 'get_bloom_filter_settings()'Taylor Blau, Aug 3, 2020
  3. Jeff KingAug 4, 2020
  4. Taylor BlauAug 4, 2020
  5. 02/10 commit-graph: pass a 'struct repository *' in more placesTaylor Blau, Aug 3, 2020
  6. 03/10 t4216: use an '&&'-chainTaylor Blau, Aug 3, 2020
  7. 04/10 t/helper/test-read-graph.c: prepare repo settingsTaylor Blau, Aug 3, 2020
  8. 05/10 commit-graph: respect 'commitgraph.readChangedPaths'Taylor Blau, Aug 3, 2020
  9. 06/10 commit-graph.c: sort index into commits listTaylor Blau, Aug 3, 2020
  10. Derrick StoleeAug 4, 2020
  11. Taylor BlauAug 4, 2020
  12. 07/10 commit-graph: add large-filters bitmap chunkTaylor Blau, Aug 3, 2020
  13. Taylor BlauAug 3, 2020
  14. Derrick StoleeAug 4, 2020
  15. 08/10 bloom: split 'get_bloom_filter()' in twoTaylor Blau, Aug 3, 2020
  16. Derrick StoleeAug 4, 2020
  17. Taylor BlauAug 4, 2020
  18. 09/10 commit-graph: rename 'split_commit_graph_opts'Taylor Blau, Aug 3, 2020
  19. 10/10 builtin/commit-graph.c: introduce '--max-new-filters=<n>'Taylor Blau, Aug 3, 2020
  20. Derrick StoleeAug 4, 2020
  21. Taylor BlauAug 4, 2020
  22. 00/14 more miscellaneous Bloom filter improvementsTaylor Blau, Aug 5, 2020
  23. 01/14 commit-graph: introduce 'get_bloom_filter_settings()'Taylor Blau, Aug 5, 2020
  24. 02/14 t4216: use an '&&'-chainTaylor Blau, Aug 5, 2020
  25. 09/14 bloom/diff: properly short-circuit on max_changesTaylor Blau, Aug 5, 2020
  26. 10/14 commit-graph.c: sort index into commits listTaylor Blau, Aug 5, 2020
  27. 08/14 bloom: use provided 'struct bloom_filter_settings'Taylor Blau, Aug 5, 2020
  28. 07/14 bloom: split 'get_bloom_filter()' in twoTaylor Blau, Aug 5, 2020
  29. 12/14 commit-graph: add large-filters bitmap chunkTaylor Blau, Aug 5, 2020
  30. Junio C HamanoAug 5, 2020
  31. Taylor BlauAug 5, 2020
  32. Junio C HamanoAug 5, 2020
  33. Taylor BlauAug 5, 2020
  34. Taylor BlauAug 11, 2020
  35. Junio C HamanoAug 11, 2020
  36. 11/14 csum-file.h: introduce 'hashwrite_be64()'Taylor Blau, Aug 5, 2020
  37. 13/14 commit-graph: rename 'split_commit_graph_opts'Taylor Blau, Aug 5, 2020
  38. 03/14 commit-graph: pass a 'struct repository *' in more placesTaylor Blau, Aug 5, 2020
  39. 06/14 commit-graph.c: store maximum changed pathsTaylor Blau, Aug 5, 2020
  40. 04/14 t/helper/test-read-graph.c: prepare repo settingsTaylor Blau, Aug 5, 2020
  41. 05/14 commit-graph: respect 'commitGraph.readChangedPaths'Taylor Blau, Aug 5, 2020
  42. 14/14 builtin/commit-graph.c: introduce '--max-new-filters=<n>'Taylor Blau, Aug 5, 2020
  43. 00/14 more miscellaneous Bloom filter improvementsTaylor Blau, Aug 11, 2020
  44. 01/14 commit-graph: introduce 'get_bloom_filter_settings()'Taylor Blau, Aug 11, 2020
  45. SZEDER GáborAug 11, 2020
  46. Taylor BlauAug 11, 2020
  47. SZEDER GáborAug 11, 2020
  48. Taylor BlauAug 11, 2020
  49. SZEDER GáborAug 11, 2020
  50. Derrick StoleeAug 12, 2020
  51. Taylor BlauAug 14, 2020
  52. 02/14 t4216: use an '&&'-chainTaylor Blau, Aug 11, 2020
  53. 03/14 commit-graph: pass a 'struct repository *' in more placesTaylor Blau, Aug 11, 2020
  54. 04/14 t/helper/test-read-graph.c: prepare repo settingsTaylor Blau, Aug 11, 2020
  55. 05/14 commit-graph: respect 'commitGraph.readChangedPaths'Taylor Blau, Aug 11, 2020
  56. 06/14 commit-graph.c: store maximum changed pathsTaylor Blau, Aug 11, 2020
  57. 07/14 bloom: split 'get_bloom_filter()' in twoTaylor Blau, Aug 11, 2020
  58. 11/14 csum-file.h: introduce 'hashwrite_be64()'Taylor Blau, Aug 11, 2020
  59. 08/14 bloom: use provided 'struct bloom_filter_settings'Taylor Blau, Aug 11, 2020
  60. 09/14 bloom/diff: properly short-circuit on max_changesTaylor Blau, Aug 11, 2020
  61. 10/14 commit-graph.c: sort index into commits listTaylor Blau, Aug 11, 2020
  62. 12/14 commit-graph: add large-filters bitmap chunkTaylor Blau, Aug 11, 2020
  63. Derrick StoleeAug 11, 2020
  64. Taylor BlauAug 11, 2020
  65. Taylor BlauAug 11, 2020
  66. SZEDER GáborAug 19, 2020
  67. Taylor BlauSep 2, 2020
  68. SZEDER GáborSep 1, 2020
  69. Taylor BlauSep 2, 2020
  70. 13/14 commit-graph: rename 'split_commit_graph_opts'Taylor Blau, Aug 11, 2020
  71. SZEDER GáborAug 19, 2020
  72. Taylor BlauSep 2, 2020
  73. 14/14 builtin/commit-graph.c: introduce '--max-new-filters=<n>'Taylor Blau, Aug 11, 2020
  74. SZEDER GáborAug 12, 2020
  75. Taylor BlauAug 14, 2020
  76. SZEDER GáborAug 17, 2020
  77. Taylor BlauSep 2, 2020
  78. Derrick StoleeAug 12, 2020
  79. Taylor BlauAug 14, 2020
  80. SZEDER GáborAug 18, 2020
  81. Taylor BlauSep 3, 2020
  82. SZEDER GáborAug 19, 2020
  83. Taylor BlauSep 3, 2020
  84. SZEDER GáborSep 4, 2020
  85. SZEDER GáborSep 1, 2020
  86. Taylor BlauSep 3, 2020
  87. Junio C HamanoSep 3, 2020
  88. Taylor BlauSep 3, 2020
  89. 00/14 more miscellaneous Bloom filter improvementsTaylor Blau, Sep 3, 2020
  90. 01/14 commit-graph: introduce 'get_bloom_filter_settings()'Taylor Blau, Sep 3, 2020
  91. 02/14 t4216: use an '&&'-chainTaylor Blau, Sep 3, 2020
  92. 04/14 t/helper/test-read-graph.c: prepare repo settingsTaylor Blau, Sep 3, 2020
  93. 03/14 commit-graph: pass a 'struct repository *' in more placesTaylor Blau, Sep 3, 2020
  94. 05/14 commit-graph: respect 'commitGraph.readChangedPaths'Taylor Blau, Sep 3, 2020
  95. 06/14 commit-graph.c: store maximum changed pathsTaylor Blau, Sep 3, 2020
  96. 07/14 bloom: split 'get_bloom_filter()' in twoTaylor Blau, Sep 3, 2020
  97. Jakub NarębskiSep 5, 2020
  98. Taylor BlauSep 5, 2020
  99. Jakub NarębskiSep 5, 2020
  100. Taylor BlauSep 5, 2020
  101. Jakub NarębskiSep 5, 2020
  102. Taylor BlauSep 5, 2020
  103. Taylor BlauSep 5, 2020
  104. SZEDER GáborSep 5, 2020
  105. Taylor BlauSep 5, 2020
  106. Junio C HamanoSep 6, 2020
  107. 08/14 bloom: use provided 'struct bloom_filter_settings'Taylor Blau, Sep 3, 2020
  108. 09/14 bloom/diff: properly short-circuit on max_changesTaylor Blau, Sep 3, 2020
  109. 10/14 commit-graph.c: sort index into commits listTaylor Blau, Sep 3, 2020
  110. 11/14 csum-file.h: introduce 'hashwrite_be64()'Taylor Blau, Sep 3, 2020
  111. René ScharfeSep 4, 2020
  112. Taylor BlauSep 4, 2020
  113. 12/14 commit-graph: add large-filters bitmap chunkTaylor Blau, Sep 3, 2020
  114. 13/14 commit-graph: rename 'split_commit_graph_opts'Taylor Blau, Sep 3, 2020
  115. Taylor BlauSep 4, 2020
  116. 14/14 builtin/commit-graph.c: introduce '--max-new-filters=<n>'Taylor Blau, Sep 3, 2020
  117. Derrick StoleeSep 4, 2020

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