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[PATCH v2 00/11] More commit-graph/Bloom filter improvements

From
Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date
Jun 23, 2020, 17:46 UTC
Message-ID
<pull.659.v2.git.1592934430.gitgitgadget@gmail.com>
In-Reply-To
<pull.659.git.1592252093.gitgitgadget@gmail.com>

This builds on sg/commit-graph-cleanups, which took several patches from Szeder's series [1] and applied them almost directly to a more-recent version of Git [2].

[1] https://lore.kernel.org/git/20200529085038.26008-1-szeder.dev@gmail.com/ [2] https://lore.kernel.org/git/pull.650.git.1591362032.gitgitgadget@gmail.com/

This series adds a few extra improvements, several of which are rooted in Szeder's original series. I maintained his authorship and sign-off, even though the patches did not apply or cherry-pick at all.

(In v2, I have removed the range-diff comparison to Szeder's series, so look at the v1 cover letter for that.)

The patches have been significantly reordered. René pointed out (and Szeder discovered in the old thread) that we are not re-using the bloom_filter_settings from the existing commit-graph when writing a new one.

 1. commit-graph: place bloom_settings in context
 2. commit-graph: change test to die on parse, not load

These are mostly the same, except we now use a pointer to the settings in the commit-graph write context.

 3. bloom: get_bloom_filter() cleanups

This new patch is a subtle change in behavior that will become relevant in the very next patch. In fact, if we swap patch 3 and 4, then t4216-log-bloom.sh fails with a segfault due to a NULL filter.

 4. commit-graph: persist existence of changed-paths
This patch is now updated to use the existing changed-path filter settings.
 5. commit-graph: unify the signatures of all write_graph_chunk_*()
    functions
 6. commit-graph: simplify chunk writes into loop
 7. commit-graph: check chunk sizes after writing
These are all the same as before.
 8. revision.c: fix whitespace
This patch is the cleanup part of Taylor's patch.
 9. revision: empty pathspecs should not use Bloom filters
Here is Taylor's fix for empty pathspecs.
 10. commit-graph: check all leading directories in changed path Bloom
     filters
 11. bloom: enforce a minimum size of 8 bytes

Finally, we get these performance patches. Patch 10 is updated to have the better logic around directory separators and empty paths. Also, the list of Bloom keys is ordered with the deepest path first. That has some tiny performance benefits for deep paths since we can short-circuit the multi-key checks more often. That code path is much faster than the tree parsing, so it is hard to measure any change.

Thanks, -Stolee
Derrick Stolee (6):
  commit-graph: place bloom_settings in context
  commit-graph: change test to die on parse, not load
  bloom: get_bloom_filter() cleanups
  commit-graph: persist existence of changed-paths
  revision.c: fix whitespace
  bloom: enforce a minimum size of 8 bytes
SZEDER Gábor (4):
  commit-graph: unify the signatures of all write_graph_chunk_*()
    functions
  commit-graph: simplify chunk writes into loop
  commit-graph: check chunk sizes after writing
  commit-graph: check all leading directories in changed path Bloom
    filters
Taylor Blau (1):
  revision: empty pathspecs should not use Bloom filters
 Documentation/git-commit-graph.txt |   5 +-
 bloom.c                            |  19 ++--
 builtin/commit-graph.c             |   5 +-
 commit-graph.c                     | 136 +++++++++++++++++++++--------
 commit-graph.h                     |   3 +-
 revision.c                         |  53 ++++++++---
 revision.h                         |   6 +-
 t/t4216-log-bloom.sh               |  35 +++++++-
 t/t5318-commit-graph.sh            |   2 +-
 9 files changed, 200 insertions(+), 64 deletions(-)
base-commit: 7fbfe07ab4d4e58c0971dac73001b89f180a0af3
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-659%2Fderrickstolee%2Fbloom-2-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-659/derrickstolee/bloom-2-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/659
Range-diff vs v1:
  1:  c966969071 !  1:  57002040bc commit-graph: place bloom_settings in context
     @@ Commit message
          to combine the function prototypes and use function pointers to
          simplify write_commit_graph_file().
      
     +    By using a pointer, we can later replace the settings to match those
     +    that exist in the current commit-graph, in case a future Git version
     +    allows customization of these parameters.
     +
          Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
          Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
      
     @@ commit-graph.c: struct write_commit_graph_context {
       
       	const struct split_commit_graph_opts *split_opts;
       	size_t total_bloom_filter_data_size;
     -+	struct bloom_filter_settings bloom_settings;
     ++	const struct bloom_filter_settings *bloom_settings;
       };
       
       static void write_graph_chunk_fanout(struct hashfile *f,
     @@ commit-graph.c: static void write_graph_chunk_bloom_data(struct hashfile *f,
      -	hashwrite_be32(f, settings->hash_version);
      -	hashwrite_be32(f, settings->num_hashes);
      -	hashwrite_be32(f, settings->bits_per_entry);
     -+	hashwrite_be32(f, ctx->bloom_settings.hash_version);
     -+	hashwrite_be32(f, ctx->bloom_settings.num_hashes);
     -+	hashwrite_be32(f, ctx->bloom_settings.bits_per_entry);
     ++	hashwrite_be32(f, ctx->bloom_settings->hash_version);
     ++	hashwrite_be32(f, ctx->bloom_settings->num_hashes);
     ++	hashwrite_be32(f, ctx->bloom_settings->bits_per_entry);
       
       	while (list < last) {
       		struct bloom_filter *filter = get_bloom_filter(ctx->r, *list, 0);
     @@ commit-graph.c: static int write_commit_graph_file(struct write_commit_graph_con
       	struct object_id file_hash;
       	const struct bloom_filter_settings bloom_settings = DEFAULT_BLOOM_FILTER_SETTINGS;
       
     -+	ctx->bloom_settings = bloom_settings;
     ++	ctx->bloom_settings = &bloom_settings;
      +
       	if (ctx->split) {
       		struct strbuf tmp_file = STRBUF_INIT;
  7:  60bbc15d24 =  2:  6b63f9bd8a commit-graph: change test to die on parse, not load
  -:  ---------- >  3:  492deaf916 bloom: get_bloom_filter() cleanups
  8:  db5b8fe843 !  4:  8727b25468 commit-graph: persist existence of changed-paths
     @@ Commit message
          property of "my commit-graph has changed-path filters" automatically. A
          user can drop filters using the --no-changed-paths option.
      
     +    In the process, we need to be extremely careful to match the Bloom
     +    filter settings as specified by the commit-graph. This will allow future
     +    versions of Git to customize these settings, and the version with this
     +    change will persist those settings as commit-graphs are rewritten on
     +    top.
     +
     +    Use the trace2 API to signal the settings used during the write, and
     +    check that output in a test after manually adjusting the correct bytes
     +    in the commit-graph file.
     +
          Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
      
       ## Documentation/git-commit-graph.txt ##
     @@ builtin/commit-graph.c: static int graph_write(int argc, const char **argv)
       
      
       ## commit-graph.c ##
     +@@
     + #include "progress.h"
     + #include "bloom.h"
     + #include "commit-slab.h"
     ++#include "json-writer.h"
     ++#include "trace2.h"
     + 
     + void git_test_write_commit_graph_or_die(void)
     + {
     +@@ commit-graph.c: static void write_graph_chunk_bloom_indexes(struct hashfile *f,
     + 	stop_progress(&progress);
     + }
     + 
     ++static void trace2_bloom_filter_settings(struct write_commit_graph_context *ctx)
     ++{
     ++	struct json_writer jw = JSON_WRITER_INIT;
     ++
     ++	jw_object_begin(&jw, 0);
     ++	jw_object_intmax(&jw, "hash_version", ctx->bloom_settings->hash_version);
     ++	jw_object_intmax(&jw, "num_hashes", ctx->bloom_settings->num_hashes);
     ++	jw_object_intmax(&jw, "bits_per_entry", ctx->bloom_settings->bits_per_entry);
     ++	jw_end(&jw);
     ++
     ++	trace2_data_json("bloom", ctx->r, "settings", &jw);
     ++
     ++	jw_release(&jw);
     ++}
     ++
     + static void write_graph_chunk_bloom_data(struct hashfile *f,
     + 					 struct write_commit_graph_context *ctx)
     + {
     +@@ commit-graph.c: static void write_graph_chunk_bloom_data(struct hashfile *f,
     + 	struct progress *progress = NULL;
     + 	int i = 0;
     + 
     ++	trace2_bloom_filter_settings(ctx);
     ++
     + 	if (ctx->report_progress)
     + 		progress = start_delayed_progress(
     + 			_("Writing changed paths Bloom filters data"),
     +@@ commit-graph.c: static int write_commit_graph_file(struct write_commit_graph_context *ctx)
     + 	struct object_id file_hash;
     + 	const struct bloom_filter_settings bloom_settings = DEFAULT_BLOOM_FILTER_SETTINGS;
     + 
     +-	ctx->bloom_settings = &bloom_settings;
     ++	if (!ctx->bloom_settings)
     ++		ctx->bloom_settings = &bloom_settings;
     + 
     + 	if (ctx->split) {
     + 		struct strbuf tmp_file = STRBUF_INIT;
      @@ commit-graph.c: int write_commit_graph(struct object_directory *odb,
       	ctx->split = flags & COMMIT_GRAPH_WRITE_SPLIT ? 1 : 0;
       	ctx->check_oids = flags & COMMIT_GRAPH_WRITE_CHECK_OIDS ? 1 : 0;
     @@ commit-graph.c: int write_commit_graph(struct object_directory *odb,
       
      +	if (flags & COMMIT_GRAPH_WRITE_BLOOM_FILTERS)
      +		ctx->changed_paths = 1;
     -+	else if (!(flags & COMMIT_GRAPH_NO_WRITE_BLOOM_FILTERS)) {
     ++	if (!(flags & COMMIT_GRAPH_NO_WRITE_BLOOM_FILTERS)) {
     ++		struct commit_graph *g;
      +		prepare_commit_graph_one(ctx->r, ctx->odb);
      +
     ++		g = ctx->r->objects->commit_graph;
     ++
      +		/* We have changed-paths already. Keep them in the next graph */
     -+		if (ctx->r->objects->commit_graph &&
     -+		    ctx->r->objects->commit_graph->chunk_bloom_data)
     ++		if (g && g->chunk_bloom_data) {
      +			ctx->changed_paths = 1;
     ++			ctx->bloom_settings = g->bloom_filter_settings;
     ++		}
      +	}
      +
       	if (ctx->split) {
     @@ t/t4216-log-bloom.sh: test_expect_success 'setup - add commit-graph to the chain
       	test_line_count = 2 .git/objects/info/commit-graphs/commit-graph-chain
       '
       
     +@@ t/t4216-log-bloom.sh: test_expect_success 'Use Bloom filters if they exist in the latest but not all c
     + 	test_bloom_filters_used_when_some_filters_are_missing "-- A/B"
     + '
     + 
     ++BASE_BDAT_OFFSET=2240
     ++BASE_K_BYTE_OFFSET=$((BASE_BDAT_OFFSET + 10))
     ++BASE_LEN_BYTE_OFFSET=$((BASE_BDAT_OFFSET + 14))
     ++
     ++corrupt_graph() {
     ++	pos=$1
     ++	data="${2:-\0}"
     ++	grepstr=$3
     ++	orig_size=$(wc -c < .git/objects/info/commit-graph) &&
     ++	zero_pos=${4:-${orig_size}} &&
     ++	printf "$data" | dd of=".git/objects/info/commit-graph" bs=1 seek="$pos" conv=notrunc &&
     ++	dd of=".git/objects/info/commit-graph" bs=1 seek="$zero_pos" if=/dev/null
     ++}
     ++
     ++test_expect_success 'persist filter settings' '
     ++	test_when_finished rm -rf .git/objects/info/commit-graph* &&
     ++	GIT_TRACE2_EVENT="$(pwd)/trace2.txt" git commit-graph write --reachable --changed-paths &&
     ++	grep "{\"hash_version\":1,\"num_hashes\":7,\"bits_per_entry\":10}" trace2.txt &&
     ++	cp .git/objects/info/commit-graph commit-graph-before &&
     ++	corrupt_graph $BASE_K_BYTE_OFFSET "\09" &&
     ++	corrupt_graph $BASE_LEN_BYTE_OFFSET "\0F" &&
     ++	cp .git/objects/info/commit-graph commit-graph-after &&
     ++	test_commit c18 A/corrupt &&
     ++	GIT_TRACE2_EVENT="$(pwd)/trace2.txt" git commit-graph write --reachable --changed-paths &&
     ++	grep "{\"hash_version\":1,\"num_hashes\":57,\"bits_per_entry\":70}" trace2.txt
     ++'
     ++
     + test_done
     + \ No newline at end of file
  2:  65eb15221c !  5:  244668fec4 commit-graph: unify the signatures of all write_graph_chunk_*() functions
     @@ Commit message
      
       ## commit-graph.c ##
      @@ commit-graph.c: struct write_commit_graph_context {
     - 	struct bloom_filter_settings bloom_settings;
     + 	const struct bloom_filter_settings *bloom_settings;
       };
       
      -static void write_graph_chunk_fanout(struct hashfile *f,
     @@ commit-graph.c: static void write_graph_chunk_bloom_indexes(struct hashfile *f,
      +	return 0;
       }
       
     + static void trace2_bloom_filter_settings(struct write_commit_graph_context *ctx)
     +@@ commit-graph.c: static void trace2_bloom_filter_settings(struct write_commit_graph_context *ctx)
     + 	jw_release(&jw);
     + }
     + 
      -static void write_graph_chunk_bloom_data(struct hashfile *f,
      -					 struct write_commit_graph_context *ctx)
      +static int write_graph_chunk_bloom_data(struct hashfile *f,
  3:  3d24b9802d =  6:  8b959f2f37 commit-graph: simplify chunk writes into loop
  4:  bdca834e6d =  7:  3eb10933dc commit-graph: check chunk sizes after writing
  -:  ---------- >  8:  0bcfc1f051 revision.c: fix whitespace
  -:  ---------- >  9:  719c7091a7 revision: empty pathspecs should not use Bloom filters
  5:  9975fc96f1 ! 10:  9c2076b4ce commit-graph: check all leading directories in changed path Bloom filters
     @@ Commit message
          This adjusts the tracing values in t4216-log-bloom.sh, which provides a
          concrete way to notice the improvement.
      
     +    Helped-by: Taylor Blau <me@ttaylorr.com>
     +    Helped-by: René Scharfe <l.s.r@web.de>
          Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
          Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
      
     @@ revision.c: static void prepare_to_use_bloom_filter(struct rev_info *revs)
       	int last_index;
      -	int len;
      +	size_t len;
     -+	int path_component_nr = 0, j;
     ++	int path_component_nr = 1;
       
       	if (!revs->commits)
       		return;
      @@ revision.c: static void prepare_to_use_bloom_filter(struct rev_info *revs)
     - 
     - 	len = strlen(path);
     + 		return;
     + 	}
       
      -	revs->bloom_key = xmalloc(sizeof(struct bloom_key));
      -	fill_bloom_key(path, len, revs->bloom_key, revs->bloom_filter_settings);
      +	p = path;
     -+	do {
     -+		p = strchrnul(p + 1, '/');
     -+		path_component_nr++;
     -+	} while (p - path < len);
     ++	while (*p) {
     ++		if (is_dir_sep(*p))
     ++			path_component_nr++;
     ++		p++;
     ++	}
      +
      +	revs->bloom_keys_nr = path_component_nr;
      +	ALLOC_ARRAY(revs->bloom_keys, revs->bloom_keys_nr);
      +
     -+	p = path;
     -+	for (j = 0; j < revs->bloom_keys_nr; j++) {
     -+		p = strchrnul(p + 1, '/');
     ++	fill_bloom_key(path, len, &revs->bloom_keys[0],
     ++		       revs->bloom_filter_settings);
     ++	path_component_nr = 1;
      +
     -+		fill_bloom_key(path, p - path, &revs->bloom_keys[j],
     -+			       revs->bloom_filter_settings);
     ++	p = path + len - 1;
     ++	while (p > path) {
     ++		if (is_dir_sep(*p))
     ++			fill_bloom_key(path, p - path,
     ++				       &revs->bloom_keys[path_component_nr++],
     ++				       revs->bloom_filter_settings);
     ++		p--;
      +	}
       
       	if (trace2_is_enabled() && !bloom_filter_atexit_registered) {
  6:  2a5f1e1752 = 11:  1022c0ad21 bloom: enforce a minimum size of 8 bytes
-- 
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Message 21 of 76 in “More commit-graph/Bloom filter improvements”
  1. 0/8 More commit-graph/Bloom filter improvementsDerrick Stolee via GitGitGadget, Jun 15, 2020
  2. 2/8 commit-graph: unify the signatures of all write_graph_chunk_*() functionsSZEDER Gábor via GitGitGadget, Jun 15, 2020
  3. René ScharfeJun 18, 2020
  4. 1/8 commit-graph: place bloom_settings in contextDerrick Stolee via GitGitGadget, Jun 15, 2020
  5. René ScharfeJun 18, 2020
  6. Derrick StoleeJun 19, 2020
  7. 3/8 commit-graph: simplify chunk writes into loopSZEDER Gábor via GitGitGadget, Jun 15, 2020
  8. René ScharfeJun 18, 2020
  9. 6/8 bloom: enforce a minimum size of 8 bytesDerrick Stolee via GitGitGadget, Jun 15, 2020
  10. 7/8 commit-graph: change test to die on parse, not loadDerrick Stolee via GitGitGadget, Jun 15, 2020
  11. 8/8 commit-graph: persist existence of changed-pathsDerrick Stolee via GitGitGadget, Jun 15, 2020
  12. 5/8 commit-graph: check all leading directories in changed path Bloom filtersSZEDER Gábor via GitGitGadget, Jun 15, 2020
  13. René ScharfeJun 18, 2020
  14. René ScharfeJun 19, 2020
  15. Taylor BlauJun 19, 2020
  16. Taylor BlauJun 19, 2020
  17. Derrick StoleeJun 23, 2020
  18. 4/8 commit-graph: check chunk sizes after writingSZEDER Gábor via GitGitGadget, Jun 15, 2020
  19. Junio C HamanoJun 17, 2020
  20. Derrick StoleeJun 18, 2020
  21. 00/11 More commit-graph/Bloom filter improvementsDerrick Stolee via GitGitGadget, Jun 23, 2020
  22. 01/11 commit-graph: place bloom_settings in contextDerrick Stolee via GitGitGadget, Jun 23, 2020
  23. 03/11 bloom: get_bloom_filter() cleanupsDerrick Stolee via GitGitGadget, Jun 23, 2020
  24. René ScharfeJun 25, 2020
  25. 02/11 commit-graph: change test to die on parse, not loadDerrick Stolee via GitGitGadget, Jun 23, 2020
  26. 04/11 commit-graph: persist existence of changed-pathsDerrick Stolee via GitGitGadget, Jun 23, 2020
  27. 05/11 commit-graph: unify the signatures of all write_graph_chunk_*() functionsSZEDER Gábor via GitGitGadget, Jun 23, 2020
  28. René ScharfeJun 25, 2020
  29. 06/11 commit-graph: simplify chunk writes into loopSZEDER Gábor via GitGitGadget, Jun 23, 2020
  30. René ScharfeJun 25, 2020
  31. Derrick StoleeJun 25, 2020
  32. 08/11 revision.c: fix whitespaceDerrick Stolee via GitGitGadget, Jun 23, 2020
  33. 09/11 revision: empty pathspecs should not use Bloom filtersTaylor Blau via GitGitGadget, Jun 23, 2020
  34. 10/11 commit-graph: check all leading directories in changed path Bloom filtersSZEDER Gábor via GitGitGadget, Jun 23, 2020
  35. René ScharfeJun 25, 2020
  36. Derrick StoleeJun 25, 2020
  37. SZEDER GáborJun 26, 2020
  38. Derrick StoleeJun 26, 2020
  39. 11/11 bloom: enforce a minimum size of 8 bytesDerrick Stolee via GitGitGadget, Jun 23, 2020
  40. 07/11 commit-graph: check chunk sizes after writingSZEDER Gábor via GitGitGadget, Jun 23, 2020
  41. René ScharfeJun 25, 2020
  42. Derrick StoleeJun 25, 2020
  43. Junio C HamanoJun 24, 2020
  44. Derrick StoleeJun 24, 2020
  45. Junio C HamanoJun 25, 2020
  46. Derrick StoleeJun 25, 2020
  47. Junio C HamanoJun 25, 2020
  48. 00/10 More commit-graph/Bloom filter improvementsDerrick Stolee via GitGitGadget, Jun 26, 2020
  49. 02/10 commit-graph: change test to die on parse, not loadDerrick Stolee via GitGitGadget, Jun 26, 2020
  50. 01/10 commit-graph: place bloom_settings in contextDerrick Stolee via GitGitGadget, Jun 26, 2020
  51. 03/10 bloom: fix logic in get_bloom_filter()Derrick Stolee via GitGitGadget, Jun 26, 2020
  52. SZEDER GáborJun 27, 2020
  53. Derrick StoleeJun 29, 2020
  54. 04/10 commit-graph: persist existence of changed-pathsDerrick Stolee via GitGitGadget, Jun 26, 2020
  55. 05/10 commit-graph: unify the signatures of all write_graph_chunk_*() functionsSZEDER Gábor via GitGitGadget, Jun 26, 2020
  56. 06/10 commit-graph: simplify chunk writes into loopSZEDER Gábor via GitGitGadget, Jun 26, 2020
  57. 07/10 commit-graph: check chunk sizes after writingSZEDER Gábor via GitGitGadget, Jun 26, 2020
  58. 10/10 commit-graph: check all leading directories in changed path Bloom filtersSZEDER Gábor via GitGitGadget, Jun 26, 2020
  59. 09/10 revision: empty pathspecs should not use Bloom filtersTaylor Blau via GitGitGadget, Jun 26, 2020
  60. 08/10 revision.c: fix whitespaceDerrick Stolee via GitGitGadget, Jun 26, 2020
  61. 00/10 More commit-graph/Bloom filter improvementsDerrick Stolee via GitGitGadget, Jul 1, 2020
  62. 01/10 commit-graph: place bloom_settings in contextDerrick Stolee via GitGitGadget, Jul 1, 2020
  63. 02/10 commit-graph: change test to die on parse, not loadDerrick Stolee via GitGitGadget, Jul 1, 2020
  64. 03/10 bloom: fix logic in get_bloom_filter()Derrick Stolee via GitGitGadget, Jul 1, 2020
  65. 05/10 commit-graph: unify the signatures of all write_graph_chunk_*() functionsSZEDER Gábor via GitGitGadget, Jul 1, 2020
  66. 06/10 commit-graph: simplify chunk writes into loopSZEDER Gábor via GitGitGadget, Jul 1, 2020
  67. 07/10 commit-graph: check chunk sizes after writingSZEDER Gábor via GitGitGadget, Jul 1, 2020
  68. 10/10 commit-graph: check all leading directories in changed path Bloom filtersSZEDER Gábor via GitGitGadget, Jul 1, 2020
  69. 09/10 revision: empty pathspecs should not use Bloom filtersTaylor Blau via GitGitGadget, Jul 1, 2020
  70. 04/10 commit-graph: persist existence of changed-pathsDerrick Stolee via GitGitGadget, Jul 1, 2020
  71. SZEDER GáborOct 15, 2020
  72. Taylor BlauOct 15, 2020
  73. Derrick StoleeOct 16, 2020
  74. Taylor BlauOct 16, 2020
  75. Derrick StoleeOct 16, 2020
  76. 08/10 revision.c: fix whitespaceDerrick Stolee via GitGitGadget, Jul 1, 2020

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