2020-04-06 18:59:54 +02:00
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#!/bin/sh
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test_description='git log for a path with Bloom filters'
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. ./test-lib.sh
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GIT_TEST_COMMIT_GRAPH=0
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GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=0
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test_expect_success 'setup test - repo, commits, commit graph, log outputs' '
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git init &&
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mkdir A A/B A/B/C &&
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test_commit c1 A/file1 &&
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test_commit c2 A/B/file2 &&
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test_commit c3 A/B/C/file3 &&
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test_commit c4 A/file1 &&
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test_commit c5 A/B/file2 &&
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test_commit c6 A/B/C/file3 &&
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test_commit c7 A/file1 &&
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test_commit c8 A/B/file2 &&
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test_commit c9 A/B/C/file3 &&
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test_commit c10 file_to_be_deleted &&
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git checkout -b side HEAD~4 &&
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test_commit side-1 file4 &&
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git checkout master &&
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git merge side &&
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test_commit c11 file5 &&
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mv file5 file5_renamed &&
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git add file5_renamed &&
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git commit -m "rename" &&
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rm file_to_be_deleted &&
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git add . &&
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git commit -m "file removed" &&
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bloom: encode out-of-bounds filters as non-empty
When a changed-path Bloom filter has either zero, or more than a
certain number (commonly 512) of entries, the commit-graph machinery
encodes it as "missing". More specifically, it sets the indices adjacent
in the BIDX chunk as equal to each other to indicate a "length 0"
filter; that is, that the filter occupies zero bytes on disk.
This has heretofore been fine, since the commit-graph machinery has no
need to care about these filters with too few or too many changed paths.
Both cases act like no filter has been generated at all, and so there is
no need to store them.
In a subsequent commit, however, the commit-graph machinery will learn
to only compute Bloom filters for some commits in the current
commit-graph layer. This is a change from the current implementation
which computes Bloom filters for all commits that are in the layer being
written. Critically for this patch, only computing some of the Bloom
filters means adding a third state for length 0 Bloom filters: zero
entries, too many entries, or "hasn't been computed".
It will be important for that future patch to distinguish between "not
representable" (i.e., zero or too-many changed paths), and "hasn't been
computed". In particular, we don't want to waste time recomputing
filters that have already been computed.
To that end, change how we store Bloom filters in the "computed but not
representable" category:
- Bloom filters with no entries are stored as a single byte with all
bits low (i.e., all queries to that Bloom filter will return
"definitely not")
- Bloom filters with too many entries are stored as a single byte with
all bits set high (i.e., all queries to that Bloom filter will
return "maybe").
These rules are sufficient to not incur a behavior change by changing
the on-disk representation of these two classes. Likewise, no
specification changes are necessary for the commit-graph format, either:
- Filters that were previously empty will be recomputed and stored
according to the new rules, and
- old clients reading filters generated by new clients will interpret
the filters correctly and be none the wiser to how they were
generated.
Clients will invoke the Bloom machinery in more cases than before, but
this can be addressed by returning a NULL filter when all bits are set
high. This can be addressed in a future patch.
Note that this does increase the size of on-disk commit-graphs, but far
less than other proposals. In particular, this is generally more
efficient than storing a bitmap for which commits haven't computed their
Bloom filters. Storing a bitmap incurs a penalty of one bit per commit,
whereas storing explicit filters as above incurs a penalty of one byte
per too-large or empty commit.
In practice, these boundary commits likely occupy a small proportion of
the overall number of commits, and so the size penalty is likely smaller
than storing a bitmap for all commits.
See, for example, these relative proportions of such boundary commits
(collected by SZEDER Gábor):
| Percentage of | commit-graph | |
| commits modifying | file size | |
├────────┬──────────────┼───────────────────┤ pct. |
| 0 path | >= 512 paths | before | after | change |
┌────────────────┼────────┼──────────────┼─────────┼─────────┼───────────┤
| android-base | 13.20% | 0.13% | 37.468M | 37.534M | +0.1741 % |
| cmssw | 0.15% | 0.23% | 17.118M | 17.119M | +0.0091 % |
| cpython | 3.07% | 0.01% | 7.967M | 7.971M | +0.0423 % |
| elasticsearch | 0.70% | 1.00% | 8.833M | 8.835M | +0.0128 % |
| gcc | 0.00% | 0.08% | 16.073M | 16.074M | +0.0030 % |
| gecko-dev | 0.14% | 0.64% | 59.868M | 59.874M | +0.0105 % |
| git | 0.11% | 0.02% | 3.895M | 3.895M | +0.0020 % |
| glibc | 0.02% | 0.10% | 3.555M | 3.555M | +0.0021 % |
| go | 0.00% | 0.07% | 3.186M | 3.186M | +0.0018 % |
| homebrew-cask | 0.40% | 0.02% | 7.035M | 7.035M | +0.0065 % |
| homebrew-core | 0.01% | 0.01% | 11.611M | 11.611M | +0.0002 % |
| jdk | 0.26% | 5.64% | 5.537M | 5.540M | +0.0590 % |
| linux | 0.01% | 0.51% | 63.735M | 63.740M | +0.0073 % |
| llvm-project | 0.12% | 0.03% | 25.515M | 25.516M | +0.0050 % |
| rails | 0.10% | 0.10% | 6.252M | 6.252M | +0.0027 % |
| rust | 0.07% | 0.17% | 9.364M | 9.364M | +0.0033 % |
| tensorflow | 0.09% | 1.02% | 7.009M | 7.010M | +0.0158 % |
| webkit | 0.05% | 0.31% | 17.405M | 17.406M | +0.0047 % |
(where the above increase is determined by computing a non-split
commit-graph before and after this patch).
Given that these projects are all "large" by commit count, the storage
cost by writing these filters explicitly is negligible. In the most
extreme example, android-base (which has 494,848 commits at the time of
writing) would have its commit-graph increase by a modest 68.4 KB.
Finally, a test to exercise filters which contain too many changed path
entries will be introduced in a subsequent patch.
Suggested-by: SZEDER Gábor <szeder.dev@gmail.com>
Suggested-by: Jakub Narębski <jnareb@gmail.com>
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Helped-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-18 04:59:44 +02:00
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git commit --allow-empty -m "empty" &&
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2020-08-17 16:04:47 +02:00
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git commit-graph write --reachable --changed-paths &&
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test_oid_cache <<-EOF
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oid_version sha1:1
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oid_version sha256:2
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EOF
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2020-04-06 18:59:54 +02:00
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'
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bloom: encode out-of-bounds filters as non-empty
When a changed-path Bloom filter has either zero, or more than a
certain number (commonly 512) of entries, the commit-graph machinery
encodes it as "missing". More specifically, it sets the indices adjacent
in the BIDX chunk as equal to each other to indicate a "length 0"
filter; that is, that the filter occupies zero bytes on disk.
This has heretofore been fine, since the commit-graph machinery has no
need to care about these filters with too few or too many changed paths.
Both cases act like no filter has been generated at all, and so there is
no need to store them.
In a subsequent commit, however, the commit-graph machinery will learn
to only compute Bloom filters for some commits in the current
commit-graph layer. This is a change from the current implementation
which computes Bloom filters for all commits that are in the layer being
written. Critically for this patch, only computing some of the Bloom
filters means adding a third state for length 0 Bloom filters: zero
entries, too many entries, or "hasn't been computed".
It will be important for that future patch to distinguish between "not
representable" (i.e., zero or too-many changed paths), and "hasn't been
computed". In particular, we don't want to waste time recomputing
filters that have already been computed.
To that end, change how we store Bloom filters in the "computed but not
representable" category:
- Bloom filters with no entries are stored as a single byte with all
bits low (i.e., all queries to that Bloom filter will return
"definitely not")
- Bloom filters with too many entries are stored as a single byte with
all bits set high (i.e., all queries to that Bloom filter will
return "maybe").
These rules are sufficient to not incur a behavior change by changing
the on-disk representation of these two classes. Likewise, no
specification changes are necessary for the commit-graph format, either:
- Filters that were previously empty will be recomputed and stored
according to the new rules, and
- old clients reading filters generated by new clients will interpret
the filters correctly and be none the wiser to how they were
generated.
Clients will invoke the Bloom machinery in more cases than before, but
this can be addressed by returning a NULL filter when all bits are set
high. This can be addressed in a future patch.
Note that this does increase the size of on-disk commit-graphs, but far
less than other proposals. In particular, this is generally more
efficient than storing a bitmap for which commits haven't computed their
Bloom filters. Storing a bitmap incurs a penalty of one bit per commit,
whereas storing explicit filters as above incurs a penalty of one byte
per too-large or empty commit.
In practice, these boundary commits likely occupy a small proportion of
the overall number of commits, and so the size penalty is likely smaller
than storing a bitmap for all commits.
See, for example, these relative proportions of such boundary commits
(collected by SZEDER Gábor):
| Percentage of | commit-graph | |
| commits modifying | file size | |
├────────┬──────────────┼───────────────────┤ pct. |
| 0 path | >= 512 paths | before | after | change |
┌────────────────┼────────┼──────────────┼─────────┼─────────┼───────────┤
| android-base | 13.20% | 0.13% | 37.468M | 37.534M | +0.1741 % |
| cmssw | 0.15% | 0.23% | 17.118M | 17.119M | +0.0091 % |
| cpython | 3.07% | 0.01% | 7.967M | 7.971M | +0.0423 % |
| elasticsearch | 0.70% | 1.00% | 8.833M | 8.835M | +0.0128 % |
| gcc | 0.00% | 0.08% | 16.073M | 16.074M | +0.0030 % |
| gecko-dev | 0.14% | 0.64% | 59.868M | 59.874M | +0.0105 % |
| git | 0.11% | 0.02% | 3.895M | 3.895M | +0.0020 % |
| glibc | 0.02% | 0.10% | 3.555M | 3.555M | +0.0021 % |
| go | 0.00% | 0.07% | 3.186M | 3.186M | +0.0018 % |
| homebrew-cask | 0.40% | 0.02% | 7.035M | 7.035M | +0.0065 % |
| homebrew-core | 0.01% | 0.01% | 11.611M | 11.611M | +0.0002 % |
| jdk | 0.26% | 5.64% | 5.537M | 5.540M | +0.0590 % |
| linux | 0.01% | 0.51% | 63.735M | 63.740M | +0.0073 % |
| llvm-project | 0.12% | 0.03% | 25.515M | 25.516M | +0.0050 % |
| rails | 0.10% | 0.10% | 6.252M | 6.252M | +0.0027 % |
| rust | 0.07% | 0.17% | 9.364M | 9.364M | +0.0033 % |
| tensorflow | 0.09% | 1.02% | 7.009M | 7.010M | +0.0158 % |
| webkit | 0.05% | 0.31% | 17.405M | 17.406M | +0.0047 % |
(where the above increase is determined by computing a non-split
commit-graph before and after this patch).
Given that these projects are all "large" by commit count, the storage
cost by writing these filters explicitly is negligible. In the most
extreme example, android-base (which has 494,848 commits at the time of
writing) would have its commit-graph increase by a modest 68.4 KB.
Finally, a test to exercise filters which contain too many changed path
entries will be introduced in a subsequent patch.
Suggested-by: SZEDER Gábor <szeder.dev@gmail.com>
Suggested-by: Jakub Narębski <jnareb@gmail.com>
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Helped-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-18 04:59:44 +02:00
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2020-04-06 18:59:54 +02:00
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graph_read_expect () {
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NUM_CHUNKS=5
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cat >expect <<- EOF
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2020-08-17 16:04:47 +02:00
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header: 43475048 1 $(test_oid oid_version) $NUM_CHUNKS 0
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2020-04-06 18:59:54 +02:00
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num_commits: $1
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chunks: oid_fanout oid_lookup commit_metadata bloom_indexes bloom_data
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EOF
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test-tool read-graph >actual &&
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test_cmp expect actual
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}
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test_expect_success 'commit-graph write wrote out the bloom chunks' '
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bloom: encode out-of-bounds filters as non-empty
When a changed-path Bloom filter has either zero, or more than a
certain number (commonly 512) of entries, the commit-graph machinery
encodes it as "missing". More specifically, it sets the indices adjacent
in the BIDX chunk as equal to each other to indicate a "length 0"
filter; that is, that the filter occupies zero bytes on disk.
This has heretofore been fine, since the commit-graph machinery has no
need to care about these filters with too few or too many changed paths.
Both cases act like no filter has been generated at all, and so there is
no need to store them.
In a subsequent commit, however, the commit-graph machinery will learn
to only compute Bloom filters for some commits in the current
commit-graph layer. This is a change from the current implementation
which computes Bloom filters for all commits that are in the layer being
written. Critically for this patch, only computing some of the Bloom
filters means adding a third state for length 0 Bloom filters: zero
entries, too many entries, or "hasn't been computed".
It will be important for that future patch to distinguish between "not
representable" (i.e., zero or too-many changed paths), and "hasn't been
computed". In particular, we don't want to waste time recomputing
filters that have already been computed.
To that end, change how we store Bloom filters in the "computed but not
representable" category:
- Bloom filters with no entries are stored as a single byte with all
bits low (i.e., all queries to that Bloom filter will return
"definitely not")
- Bloom filters with too many entries are stored as a single byte with
all bits set high (i.e., all queries to that Bloom filter will
return "maybe").
These rules are sufficient to not incur a behavior change by changing
the on-disk representation of these two classes. Likewise, no
specification changes are necessary for the commit-graph format, either:
- Filters that were previously empty will be recomputed and stored
according to the new rules, and
- old clients reading filters generated by new clients will interpret
the filters correctly and be none the wiser to how they were
generated.
Clients will invoke the Bloom machinery in more cases than before, but
this can be addressed by returning a NULL filter when all bits are set
high. This can be addressed in a future patch.
Note that this does increase the size of on-disk commit-graphs, but far
less than other proposals. In particular, this is generally more
efficient than storing a bitmap for which commits haven't computed their
Bloom filters. Storing a bitmap incurs a penalty of one bit per commit,
whereas storing explicit filters as above incurs a penalty of one byte
per too-large or empty commit.
In practice, these boundary commits likely occupy a small proportion of
the overall number of commits, and so the size penalty is likely smaller
than storing a bitmap for all commits.
See, for example, these relative proportions of such boundary commits
(collected by SZEDER Gábor):
| Percentage of | commit-graph | |
| commits modifying | file size | |
├────────┬──────────────┼───────────────────┤ pct. |
| 0 path | >= 512 paths | before | after | change |
┌────────────────┼────────┼──────────────┼─────────┼─────────┼───────────┤
| android-base | 13.20% | 0.13% | 37.468M | 37.534M | +0.1741 % |
| cmssw | 0.15% | 0.23% | 17.118M | 17.119M | +0.0091 % |
| cpython | 3.07% | 0.01% | 7.967M | 7.971M | +0.0423 % |
| elasticsearch | 0.70% | 1.00% | 8.833M | 8.835M | +0.0128 % |
| gcc | 0.00% | 0.08% | 16.073M | 16.074M | +0.0030 % |
| gecko-dev | 0.14% | 0.64% | 59.868M | 59.874M | +0.0105 % |
| git | 0.11% | 0.02% | 3.895M | 3.895M | +0.0020 % |
| glibc | 0.02% | 0.10% | 3.555M | 3.555M | +0.0021 % |
| go | 0.00% | 0.07% | 3.186M | 3.186M | +0.0018 % |
| homebrew-cask | 0.40% | 0.02% | 7.035M | 7.035M | +0.0065 % |
| homebrew-core | 0.01% | 0.01% | 11.611M | 11.611M | +0.0002 % |
| jdk | 0.26% | 5.64% | 5.537M | 5.540M | +0.0590 % |
| linux | 0.01% | 0.51% | 63.735M | 63.740M | +0.0073 % |
| llvm-project | 0.12% | 0.03% | 25.515M | 25.516M | +0.0050 % |
| rails | 0.10% | 0.10% | 6.252M | 6.252M | +0.0027 % |
| rust | 0.07% | 0.17% | 9.364M | 9.364M | +0.0033 % |
| tensorflow | 0.09% | 1.02% | 7.009M | 7.010M | +0.0158 % |
| webkit | 0.05% | 0.31% | 17.405M | 17.406M | +0.0047 % |
(where the above increase is determined by computing a non-split
commit-graph before and after this patch).
Given that these projects are all "large" by commit count, the storage
cost by writing these filters explicitly is negligible. In the most
extreme example, android-base (which has 494,848 commits at the time of
writing) would have its commit-graph increase by a modest 68.4 KB.
Finally, a test to exercise filters which contain too many changed path
entries will be introduced in a subsequent patch.
Suggested-by: SZEDER Gábor <szeder.dev@gmail.com>
Suggested-by: Jakub Narębski <jnareb@gmail.com>
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Helped-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-18 04:59:44 +02:00
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graph_read_expect 16
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2020-04-06 18:59:54 +02:00
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'
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# Turn off any inherited trace2 settings for this test.
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sane_unset GIT_TRACE2 GIT_TRACE2_PERF GIT_TRACE2_EVENT
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sane_unset GIT_TRACE2_PERF_BRIEF
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sane_unset GIT_TRACE2_CONFIG_PARAMS
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setup () {
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t4216: use an '&&'-chain
In a759bfa9ee (t4216: add end to end tests for git log with Bloom
filters, 2020-04-06), a 'rm' invocation was added without a
corresponding '&&' chain.
When 'trace.perf' already exists, everything works fine. However, the
function can be executed without 'trace.perf' on disk (eg., when the
subset of tests run is altered with '--run'), and so the bare 'rm'
complains about a missing file.
To remove some noise from the test log, invoke 'rm' with '-f', at which
point it is sensible to place the 'rm -f' in an '&&'-chain, which is
both (1) our usual style, and (2) avoids a broken chain in the future if
more commands are added at the beginning of the function.
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-09 17:22:50 +02:00
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rm -f "$TRASH_DIRECTORY/trace.perf" &&
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2020-04-06 18:59:54 +02:00
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git -c core.commitGraph=false log --pretty="format:%s" $1 >log_wo_bloom &&
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GIT_TRACE2_PERF="$TRASH_DIRECTORY/trace.perf" git -c core.commitGraph=true log --pretty="format:%s" $1 >log_w_bloom
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}
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test_bloom_filters_used () {
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log_args=$1
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commit-graph: introduce 'get_bloom_filter_settings()'
Many places in the code often need a pointer to the commit-graph's
'struct bloom_filter_settings', in which case they often take the value
from the top-most commit-graph.
In the non-split case, this works as expected. In the split case,
however, things get a little tricky. Not all layers in a chain of
incremental commit-graphs are required to themselves have Bloom data,
and so whether or not some part of the code uses Bloom filters depends
entirely on whether or not the top-most level of the commit-graph chain
has Bloom filters.
This has been the behavior since Bloom filters were introduced, and has
been codified into the tests since a759bfa9ee (t4216: add end to end
tests for git log with Bloom filters, 2020-04-06). In fact, t4216.130
requires that Bloom filters are not used in exactly the case described
earlier.
There is no reason that this needs to be the case, since it is perfectly
valid for commits in an earlier layer to have Bloom filters when commits
in a newer layer do not.
Since Bloom settings are guaranteed in practice to be the same for any
layer in a chain that has Bloom data, it is sufficient to traverse the
'->base_graph' pointer until either (1) a non-null 'struct
bloom_filter_settings *' is found, or (2) until we are at the root of
the commit-graph chain.
Introduce a 'get_bloom_filter_settings()' function that does just this,
and use it instead of purely dereferencing the top-most graph's
'->bloom_filter_settings' pointer.
While we're at it, add an additional test in t5324 to guard against code
in the commit-graph writing machinery that doesn't correctly handle a
NULL 'struct bloom_filter *'.
Co-authored-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-09 17:22:44 +02:00
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bloom_trace_prefix="statistics:{\"filter_not_present\":${2:-0},\"maybe\""
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2020-04-06 18:59:54 +02:00
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setup "$log_args" &&
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grep -q "$bloom_trace_prefix" "$TRASH_DIRECTORY/trace.perf" &&
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test_cmp log_wo_bloom log_w_bloom &&
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test_path_is_file "$TRASH_DIRECTORY/trace.perf"
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}
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test_bloom_filters_not_used () {
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log_args=$1
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setup "$log_args" &&
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2020-05-20 05:44:42 +02:00
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! grep -q "statistics:{\"filter_not_present\":" "$TRASH_DIRECTORY/trace.perf" &&
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2020-04-06 18:59:54 +02:00
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test_cmp log_wo_bloom log_w_bloom
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}
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|
|
for path in A A/B A/B/C A/file1 A/B/file2 A/B/C/file3 file4 file5 file5_renamed file_to_be_deleted
|
|
|
|
do
|
|
|
|
for option in "" \
|
|
|
|
"--all" \
|
|
|
|
"--full-history" \
|
|
|
|
"--full-history --simplify-merges" \
|
|
|
|
"--simplify-merges" \
|
|
|
|
"--simplify-by-decoration" \
|
|
|
|
"--follow" \
|
|
|
|
"--first-parent" \
|
|
|
|
"--topo-order" \
|
|
|
|
"--date-order" \
|
|
|
|
"--author-date-order" \
|
|
|
|
"--ancestry-path side..master"
|
|
|
|
do
|
|
|
|
test_expect_success "git log option: $option for path: $path" '
|
2020-09-09 17:23:10 +02:00
|
|
|
test_bloom_filters_used "$option -- $path" &&
|
|
|
|
test_config commitgraph.readChangedPaths false &&
|
|
|
|
test_bloom_filters_not_used "$option -- $path"
|
2020-04-06 18:59:54 +02:00
|
|
|
'
|
|
|
|
done
|
|
|
|
done
|
|
|
|
|
|
|
|
test_expect_success 'git log -- folder works with and without the trailing slash' '
|
|
|
|
test_bloom_filters_used "-- A" &&
|
|
|
|
test_bloom_filters_used "-- A/"
|
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success 'git log for path that does not exist. ' '
|
|
|
|
test_bloom_filters_used "-- path_does_not_exist"
|
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success 'git log with --walk-reflogs does not use Bloom filters' '
|
|
|
|
test_bloom_filters_not_used "--walk-reflogs -- A"
|
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success 'git log -- multiple path specs does not use Bloom filters' '
|
|
|
|
test_bloom_filters_not_used "-- file4 A/file1"
|
|
|
|
'
|
|
|
|
|
2020-07-01 15:27:29 +02:00
|
|
|
test_expect_success 'git log -- "." pathspec at root does not use Bloom filters' '
|
|
|
|
test_bloom_filters_not_used "-- ."
|
|
|
|
'
|
|
|
|
|
2020-04-06 18:59:54 +02:00
|
|
|
test_expect_success 'git log with wildcard that resolves to a single path uses Bloom filters' '
|
|
|
|
test_bloom_filters_used "-- *4" &&
|
|
|
|
test_bloom_filters_used "-- *renamed"
|
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success 'git log with wildcard that resolves to a multiple paths does not uses Bloom filters' '
|
|
|
|
test_bloom_filters_not_used "-- *" &&
|
|
|
|
test_bloom_filters_not_used "-- file*"
|
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success 'setup - add commit-graph to the chain without Bloom filters' '
|
|
|
|
test_commit c14 A/anotherFile2 &&
|
|
|
|
test_commit c15 A/B/anotherFile2 &&
|
|
|
|
test_commit c16 A/B/C/anotherFile2 &&
|
2020-07-01 15:27:24 +02:00
|
|
|
git commit-graph write --reachable --split --no-changed-paths &&
|
2020-04-06 18:59:54 +02:00
|
|
|
test_line_count = 2 .git/objects/info/commit-graphs/commit-graph-chain
|
|
|
|
'
|
|
|
|
|
commit-graph: introduce 'get_bloom_filter_settings()'
Many places in the code often need a pointer to the commit-graph's
'struct bloom_filter_settings', in which case they often take the value
from the top-most commit-graph.
In the non-split case, this works as expected. In the split case,
however, things get a little tricky. Not all layers in a chain of
incremental commit-graphs are required to themselves have Bloom data,
and so whether or not some part of the code uses Bloom filters depends
entirely on whether or not the top-most level of the commit-graph chain
has Bloom filters.
This has been the behavior since Bloom filters were introduced, and has
been codified into the tests since a759bfa9ee (t4216: add end to end
tests for git log with Bloom filters, 2020-04-06). In fact, t4216.130
requires that Bloom filters are not used in exactly the case described
earlier.
There is no reason that this needs to be the case, since it is perfectly
valid for commits in an earlier layer to have Bloom filters when commits
in a newer layer do not.
Since Bloom settings are guaranteed in practice to be the same for any
layer in a chain that has Bloom data, it is sufficient to traverse the
'->base_graph' pointer until either (1) a non-null 'struct
bloom_filter_settings *' is found, or (2) until we are at the root of
the commit-graph chain.
Introduce a 'get_bloom_filter_settings()' function that does just this,
and use it instead of purely dereferencing the top-most graph's
'->bloom_filter_settings' pointer.
While we're at it, add an additional test in t5324 to guard against code
in the commit-graph writing machinery that doesn't correctly handle a
NULL 'struct bloom_filter *'.
Co-authored-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-09 17:22:44 +02:00
|
|
|
test_expect_success 'use Bloom filters even if the latest graph does not have Bloom filters' '
|
|
|
|
# Ensure that the number of empty filters is equal to the number of
|
|
|
|
# filters in the latest graph layer to prove that they are loaded (and
|
|
|
|
# ignored).
|
|
|
|
test_bloom_filters_used "-- A/B" 3
|
2020-04-06 18:59:54 +02:00
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success 'setup - add commit-graph to the chain with Bloom filters' '
|
|
|
|
test_commit c17 A/anotherFile3 &&
|
|
|
|
git commit-graph write --reachable --changed-paths --split &&
|
|
|
|
test_line_count = 3 .git/objects/info/commit-graphs/commit-graph-chain
|
|
|
|
'
|
|
|
|
|
|
|
|
test_bloom_filters_used_when_some_filters_are_missing () {
|
|
|
|
log_args=$1
|
bloom: encode out-of-bounds filters as non-empty
When a changed-path Bloom filter has either zero, or more than a
certain number (commonly 512) of entries, the commit-graph machinery
encodes it as "missing". More specifically, it sets the indices adjacent
in the BIDX chunk as equal to each other to indicate a "length 0"
filter; that is, that the filter occupies zero bytes on disk.
This has heretofore been fine, since the commit-graph machinery has no
need to care about these filters with too few or too many changed paths.
Both cases act like no filter has been generated at all, and so there is
no need to store them.
In a subsequent commit, however, the commit-graph machinery will learn
to only compute Bloom filters for some commits in the current
commit-graph layer. This is a change from the current implementation
which computes Bloom filters for all commits that are in the layer being
written. Critically for this patch, only computing some of the Bloom
filters means adding a third state for length 0 Bloom filters: zero
entries, too many entries, or "hasn't been computed".
It will be important for that future patch to distinguish between "not
representable" (i.e., zero or too-many changed paths), and "hasn't been
computed". In particular, we don't want to waste time recomputing
filters that have already been computed.
To that end, change how we store Bloom filters in the "computed but not
representable" category:
- Bloom filters with no entries are stored as a single byte with all
bits low (i.e., all queries to that Bloom filter will return
"definitely not")
- Bloom filters with too many entries are stored as a single byte with
all bits set high (i.e., all queries to that Bloom filter will
return "maybe").
These rules are sufficient to not incur a behavior change by changing
the on-disk representation of these two classes. Likewise, no
specification changes are necessary for the commit-graph format, either:
- Filters that were previously empty will be recomputed and stored
according to the new rules, and
- old clients reading filters generated by new clients will interpret
the filters correctly and be none the wiser to how they were
generated.
Clients will invoke the Bloom machinery in more cases than before, but
this can be addressed by returning a NULL filter when all bits are set
high. This can be addressed in a future patch.
Note that this does increase the size of on-disk commit-graphs, but far
less than other proposals. In particular, this is generally more
efficient than storing a bitmap for which commits haven't computed their
Bloom filters. Storing a bitmap incurs a penalty of one bit per commit,
whereas storing explicit filters as above incurs a penalty of one byte
per too-large or empty commit.
In practice, these boundary commits likely occupy a small proportion of
the overall number of commits, and so the size penalty is likely smaller
than storing a bitmap for all commits.
See, for example, these relative proportions of such boundary commits
(collected by SZEDER Gábor):
| Percentage of | commit-graph | |
| commits modifying | file size | |
├────────┬──────────────┼───────────────────┤ pct. |
| 0 path | >= 512 paths | before | after | change |
┌────────────────┼────────┼──────────────┼─────────┼─────────┼───────────┤
| android-base | 13.20% | 0.13% | 37.468M | 37.534M | +0.1741 % |
| cmssw | 0.15% | 0.23% | 17.118M | 17.119M | +0.0091 % |
| cpython | 3.07% | 0.01% | 7.967M | 7.971M | +0.0423 % |
| elasticsearch | 0.70% | 1.00% | 8.833M | 8.835M | +0.0128 % |
| gcc | 0.00% | 0.08% | 16.073M | 16.074M | +0.0030 % |
| gecko-dev | 0.14% | 0.64% | 59.868M | 59.874M | +0.0105 % |
| git | 0.11% | 0.02% | 3.895M | 3.895M | +0.0020 % |
| glibc | 0.02% | 0.10% | 3.555M | 3.555M | +0.0021 % |
| go | 0.00% | 0.07% | 3.186M | 3.186M | +0.0018 % |
| homebrew-cask | 0.40% | 0.02% | 7.035M | 7.035M | +0.0065 % |
| homebrew-core | 0.01% | 0.01% | 11.611M | 11.611M | +0.0002 % |
| jdk | 0.26% | 5.64% | 5.537M | 5.540M | +0.0590 % |
| linux | 0.01% | 0.51% | 63.735M | 63.740M | +0.0073 % |
| llvm-project | 0.12% | 0.03% | 25.515M | 25.516M | +0.0050 % |
| rails | 0.10% | 0.10% | 6.252M | 6.252M | +0.0027 % |
| rust | 0.07% | 0.17% | 9.364M | 9.364M | +0.0033 % |
| tensorflow | 0.09% | 1.02% | 7.009M | 7.010M | +0.0158 % |
| webkit | 0.05% | 0.31% | 17.405M | 17.406M | +0.0047 % |
(where the above increase is determined by computing a non-split
commit-graph before and after this patch).
Given that these projects are all "large" by commit count, the storage
cost by writing these filters explicitly is negligible. In the most
extreme example, android-base (which has 494,848 commits at the time of
writing) would have its commit-graph increase by a modest 68.4 KB.
Finally, a test to exercise filters which contain too many changed path
entries will be introduced in a subsequent patch.
Suggested-by: SZEDER Gábor <szeder.dev@gmail.com>
Suggested-by: Jakub Narębski <jnareb@gmail.com>
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Helped-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-18 04:59:44 +02:00
|
|
|
bloom_trace_prefix="statistics:{\"filter_not_present\":3,\"maybe\":6,\"definitely_not\":9"
|
2020-04-06 18:59:54 +02:00
|
|
|
setup "$log_args" &&
|
|
|
|
grep -q "$bloom_trace_prefix" "$TRASH_DIRECTORY/trace.perf" &&
|
|
|
|
test_cmp log_wo_bloom log_w_bloom
|
|
|
|
}
|
|
|
|
|
|
|
|
test_expect_success 'Use Bloom filters if they exist in the latest but not all commit graphs in the chain.' '
|
|
|
|
test_bloom_filters_used_when_some_filters_are_missing "-- A/B"
|
|
|
|
'
|
|
|
|
|
2020-07-01 15:27:24 +02:00
|
|
|
test_expect_success 'persist filter settings' '
|
|
|
|
test_when_finished rm -rf .git/objects/info/commit-graph* &&
|
|
|
|
rm -rf .git/objects/info/commit-graph* &&
|
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace2.txt" \
|
|
|
|
GIT_TRACE2_EVENT_NESTING=5 \
|
|
|
|
GIT_TEST_BLOOM_SETTINGS_NUM_HASHES=9 \
|
|
|
|
GIT_TEST_BLOOM_SETTINGS_BITS_PER_ENTRY=15 \
|
|
|
|
git commit-graph write --reachable --changed-paths &&
|
2020-09-17 15:34:42 +02:00
|
|
|
grep "{\"hash_version\":1,\"num_hashes\":9,\"bits_per_entry\":15,\"max_changed_paths\":512" trace2.txt &&
|
2020-07-01 15:27:24 +02:00
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace2-auto.txt" \
|
|
|
|
GIT_TRACE2_EVENT_NESTING=5 \
|
|
|
|
git commit-graph write --reachable --changed-paths &&
|
2020-09-17 15:34:42 +02:00
|
|
|
grep "{\"hash_version\":1,\"num_hashes\":9,\"bits_per_entry\":15,\"max_changed_paths\":512" trace2-auto.txt
|
2020-07-01 15:27:24 +02:00
|
|
|
'
|
|
|
|
|
bloom/diff: properly short-circuit on max_changes
Commit e3696980 (diff: halt tree-diff early after max_changes,
2020-03-30) intended to create a mechanism to short-circuit a diff
calculation after a certain number of paths were modified. By
incrementing a "num_changes" counter throughout the recursive
ll_diff_tree_paths(), this was supposed to match the number of changes
that would be written into the changed-path Bloom filters.
Unfortunately, this was not implemented correctly and instead misses
simple cases like file modifications. This then does not stop very
large changed-path filters from being written (unless they add or remove
many files).
To start, change the implementation in ll_diff_tree_paths() to instead
use the global diff_queue_diff struct's 'nr' member as the count. This
is a way to simplify the logic instead of making more mistakes in the
complicated diff code.
This has a drawback: the diff_queue_diff struct only lists the paths
corresponding to blob changes, not their leading directories. Thus,
get_or_compute_bloom_filter() needs an additional check to see if the
hashmap with the leading directories becomes too large.
One reason why this was not caught by test cases was that the test in
t4216-log-bloom.sh that was supposed to check this "too many changes"
condition only checked this on the initial commit of a repository. The
old logic counted these values correctly. Update this test in a few
ways:
1. Use GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS to reduce the limit,
allowing smaller commits to engage with this logic.
2. Create several interesting cases of edits, adds, removes, and mode
changes (in the second commit). By testing both sides of the
inequality with the *_MAX_CHANGED_PATHS variable, we can see that
the count is exactly correct, so none of these changes are missed
or over-counted.
3. Use the trace2 data value filter_found_large to verify that these
commits are on the correct side of the limit.
Another way to verify the behavior is correct is through performance
tests. By testing on my local copies of the Git repository and the Linux
kernel repository, I could measure the effect of these short-circuits
when computing a fresh commit-graph file with changed-path Bloom filters
using the command
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=N time \
git commit-graph write --reachable --changed-paths
and reporting the wall time and resulting commit-graph size.
For Git, the results are
| | N=1 | N=10 | N=512 |
|--------|----------------|----------------|----------------|
| HEAD~1 | 10.90s 9.18MB | 11.11s 9.34MB | 11.31s 9.35MB |
| HEAD | 9.21s 8.62MB | 11.11s 9.29MB | 11.29s 9.34MB |
For Linux, the results are
| | N=1 | N=20 | N=512 |
|--------|----------------|---------------|---------------|
| HEAD~1 | 61.28s 64.3MB | 76.9s 72.6MB | 77.6s 72.6MB |
| HEAD | 49.44s 56.3MB | 68.7s 65.9MB | 69.2s 65.9MB |
Naturally, the improvement becomes much less as the limit grows, as
fewer commits satisfy the short-circuit.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-16 20:07:52 +02:00
|
|
|
test_max_changed_paths () {
|
|
|
|
grep "\"max_changed_paths\":$1" $2
|
|
|
|
}
|
|
|
|
|
bloom: encode out-of-bounds filters as non-empty
When a changed-path Bloom filter has either zero, or more than a
certain number (commonly 512) of entries, the commit-graph machinery
encodes it as "missing". More specifically, it sets the indices adjacent
in the BIDX chunk as equal to each other to indicate a "length 0"
filter; that is, that the filter occupies zero bytes on disk.
This has heretofore been fine, since the commit-graph machinery has no
need to care about these filters with too few or too many changed paths.
Both cases act like no filter has been generated at all, and so there is
no need to store them.
In a subsequent commit, however, the commit-graph machinery will learn
to only compute Bloom filters for some commits in the current
commit-graph layer. This is a change from the current implementation
which computes Bloom filters for all commits that are in the layer being
written. Critically for this patch, only computing some of the Bloom
filters means adding a third state for length 0 Bloom filters: zero
entries, too many entries, or "hasn't been computed".
It will be important for that future patch to distinguish between "not
representable" (i.e., zero or too-many changed paths), and "hasn't been
computed". In particular, we don't want to waste time recomputing
filters that have already been computed.
To that end, change how we store Bloom filters in the "computed but not
representable" category:
- Bloom filters with no entries are stored as a single byte with all
bits low (i.e., all queries to that Bloom filter will return
"definitely not")
- Bloom filters with too many entries are stored as a single byte with
all bits set high (i.e., all queries to that Bloom filter will
return "maybe").
These rules are sufficient to not incur a behavior change by changing
the on-disk representation of these two classes. Likewise, no
specification changes are necessary for the commit-graph format, either:
- Filters that were previously empty will be recomputed and stored
according to the new rules, and
- old clients reading filters generated by new clients will interpret
the filters correctly and be none the wiser to how they were
generated.
Clients will invoke the Bloom machinery in more cases than before, but
this can be addressed by returning a NULL filter when all bits are set
high. This can be addressed in a future patch.
Note that this does increase the size of on-disk commit-graphs, but far
less than other proposals. In particular, this is generally more
efficient than storing a bitmap for which commits haven't computed their
Bloom filters. Storing a bitmap incurs a penalty of one bit per commit,
whereas storing explicit filters as above incurs a penalty of one byte
per too-large or empty commit.
In practice, these boundary commits likely occupy a small proportion of
the overall number of commits, and so the size penalty is likely smaller
than storing a bitmap for all commits.
See, for example, these relative proportions of such boundary commits
(collected by SZEDER Gábor):
| Percentage of | commit-graph | |
| commits modifying | file size | |
├────────┬──────────────┼───────────────────┤ pct. |
| 0 path | >= 512 paths | before | after | change |
┌────────────────┼────────┼──────────────┼─────────┼─────────┼───────────┤
| android-base | 13.20% | 0.13% | 37.468M | 37.534M | +0.1741 % |
| cmssw | 0.15% | 0.23% | 17.118M | 17.119M | +0.0091 % |
| cpython | 3.07% | 0.01% | 7.967M | 7.971M | +0.0423 % |
| elasticsearch | 0.70% | 1.00% | 8.833M | 8.835M | +0.0128 % |
| gcc | 0.00% | 0.08% | 16.073M | 16.074M | +0.0030 % |
| gecko-dev | 0.14% | 0.64% | 59.868M | 59.874M | +0.0105 % |
| git | 0.11% | 0.02% | 3.895M | 3.895M | +0.0020 % |
| glibc | 0.02% | 0.10% | 3.555M | 3.555M | +0.0021 % |
| go | 0.00% | 0.07% | 3.186M | 3.186M | +0.0018 % |
| homebrew-cask | 0.40% | 0.02% | 7.035M | 7.035M | +0.0065 % |
| homebrew-core | 0.01% | 0.01% | 11.611M | 11.611M | +0.0002 % |
| jdk | 0.26% | 5.64% | 5.537M | 5.540M | +0.0590 % |
| linux | 0.01% | 0.51% | 63.735M | 63.740M | +0.0073 % |
| llvm-project | 0.12% | 0.03% | 25.515M | 25.516M | +0.0050 % |
| rails | 0.10% | 0.10% | 6.252M | 6.252M | +0.0027 % |
| rust | 0.07% | 0.17% | 9.364M | 9.364M | +0.0033 % |
| tensorflow | 0.09% | 1.02% | 7.009M | 7.010M | +0.0158 % |
| webkit | 0.05% | 0.31% | 17.405M | 17.406M | +0.0047 % |
(where the above increase is determined by computing a non-split
commit-graph before and after this patch).
Given that these projects are all "large" by commit count, the storage
cost by writing these filters explicitly is negligible. In the most
extreme example, android-base (which has 494,848 commits at the time of
writing) would have its commit-graph increase by a modest 68.4 KB.
Finally, a test to exercise filters which contain too many changed path
entries will be introduced in a subsequent patch.
Suggested-by: SZEDER Gábor <szeder.dev@gmail.com>
Suggested-by: Jakub Narębski <jnareb@gmail.com>
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Helped-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-18 04:59:44 +02:00
|
|
|
test_filter_not_computed () {
|
|
|
|
grep "\"key\":\"filter-not-computed\",\"value\":\"$1\"" $2
|
|
|
|
}
|
|
|
|
|
bloom/diff: properly short-circuit on max_changes
Commit e3696980 (diff: halt tree-diff early after max_changes,
2020-03-30) intended to create a mechanism to short-circuit a diff
calculation after a certain number of paths were modified. By
incrementing a "num_changes" counter throughout the recursive
ll_diff_tree_paths(), this was supposed to match the number of changes
that would be written into the changed-path Bloom filters.
Unfortunately, this was not implemented correctly and instead misses
simple cases like file modifications. This then does not stop very
large changed-path filters from being written (unless they add or remove
many files).
To start, change the implementation in ll_diff_tree_paths() to instead
use the global diff_queue_diff struct's 'nr' member as the count. This
is a way to simplify the logic instead of making more mistakes in the
complicated diff code.
This has a drawback: the diff_queue_diff struct only lists the paths
corresponding to blob changes, not their leading directories. Thus,
get_or_compute_bloom_filter() needs an additional check to see if the
hashmap with the leading directories becomes too large.
One reason why this was not caught by test cases was that the test in
t4216-log-bloom.sh that was supposed to check this "too many changes"
condition only checked this on the initial commit of a repository. The
old logic counted these values correctly. Update this test in a few
ways:
1. Use GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS to reduce the limit,
allowing smaller commits to engage with this logic.
2. Create several interesting cases of edits, adds, removes, and mode
changes (in the second commit). By testing both sides of the
inequality with the *_MAX_CHANGED_PATHS variable, we can see that
the count is exactly correct, so none of these changes are missed
or over-counted.
3. Use the trace2 data value filter_found_large to verify that these
commits are on the correct side of the limit.
Another way to verify the behavior is correct is through performance
tests. By testing on my local copies of the Git repository and the Linux
kernel repository, I could measure the effect of these short-circuits
when computing a fresh commit-graph file with changed-path Bloom filters
using the command
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=N time \
git commit-graph write --reachable --changed-paths
and reporting the wall time and resulting commit-graph size.
For Git, the results are
| | N=1 | N=10 | N=512 |
|--------|----------------|----------------|----------------|
| HEAD~1 | 10.90s 9.18MB | 11.11s 9.34MB | 11.31s 9.35MB |
| HEAD | 9.21s 8.62MB | 11.11s 9.29MB | 11.29s 9.34MB |
For Linux, the results are
| | N=1 | N=20 | N=512 |
|--------|----------------|---------------|---------------|
| HEAD~1 | 61.28s 64.3MB | 76.9s 72.6MB | 77.6s 72.6MB |
| HEAD | 49.44s 56.3MB | 68.7s 65.9MB | 69.2s 65.9MB |
Naturally, the improvement becomes much less as the limit grows, as
fewer commits satisfy the short-circuit.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-16 20:07:52 +02:00
|
|
|
test_filter_computed () {
|
|
|
|
grep "\"key\":\"filter-computed\",\"value\":\"$1\"" $2
|
|
|
|
}
|
|
|
|
|
bloom: encode out-of-bounds filters as non-empty
When a changed-path Bloom filter has either zero, or more than a
certain number (commonly 512) of entries, the commit-graph machinery
encodes it as "missing". More specifically, it sets the indices adjacent
in the BIDX chunk as equal to each other to indicate a "length 0"
filter; that is, that the filter occupies zero bytes on disk.
This has heretofore been fine, since the commit-graph machinery has no
need to care about these filters with too few or too many changed paths.
Both cases act like no filter has been generated at all, and so there is
no need to store them.
In a subsequent commit, however, the commit-graph machinery will learn
to only compute Bloom filters for some commits in the current
commit-graph layer. This is a change from the current implementation
which computes Bloom filters for all commits that are in the layer being
written. Critically for this patch, only computing some of the Bloom
filters means adding a third state for length 0 Bloom filters: zero
entries, too many entries, or "hasn't been computed".
It will be important for that future patch to distinguish between "not
representable" (i.e., zero or too-many changed paths), and "hasn't been
computed". In particular, we don't want to waste time recomputing
filters that have already been computed.
To that end, change how we store Bloom filters in the "computed but not
representable" category:
- Bloom filters with no entries are stored as a single byte with all
bits low (i.e., all queries to that Bloom filter will return
"definitely not")
- Bloom filters with too many entries are stored as a single byte with
all bits set high (i.e., all queries to that Bloom filter will
return "maybe").
These rules are sufficient to not incur a behavior change by changing
the on-disk representation of these two classes. Likewise, no
specification changes are necessary for the commit-graph format, either:
- Filters that were previously empty will be recomputed and stored
according to the new rules, and
- old clients reading filters generated by new clients will interpret
the filters correctly and be none the wiser to how they were
generated.
Clients will invoke the Bloom machinery in more cases than before, but
this can be addressed by returning a NULL filter when all bits are set
high. This can be addressed in a future patch.
Note that this does increase the size of on-disk commit-graphs, but far
less than other proposals. In particular, this is generally more
efficient than storing a bitmap for which commits haven't computed their
Bloom filters. Storing a bitmap incurs a penalty of one bit per commit,
whereas storing explicit filters as above incurs a penalty of one byte
per too-large or empty commit.
In practice, these boundary commits likely occupy a small proportion of
the overall number of commits, and so the size penalty is likely smaller
than storing a bitmap for all commits.
See, for example, these relative proportions of such boundary commits
(collected by SZEDER Gábor):
| Percentage of | commit-graph | |
| commits modifying | file size | |
├────────┬──────────────┼───────────────────┤ pct. |
| 0 path | >= 512 paths | before | after | change |
┌────────────────┼────────┼──────────────┼─────────┼─────────┼───────────┤
| android-base | 13.20% | 0.13% | 37.468M | 37.534M | +0.1741 % |
| cmssw | 0.15% | 0.23% | 17.118M | 17.119M | +0.0091 % |
| cpython | 3.07% | 0.01% | 7.967M | 7.971M | +0.0423 % |
| elasticsearch | 0.70% | 1.00% | 8.833M | 8.835M | +0.0128 % |
| gcc | 0.00% | 0.08% | 16.073M | 16.074M | +0.0030 % |
| gecko-dev | 0.14% | 0.64% | 59.868M | 59.874M | +0.0105 % |
| git | 0.11% | 0.02% | 3.895M | 3.895M | +0.0020 % |
| glibc | 0.02% | 0.10% | 3.555M | 3.555M | +0.0021 % |
| go | 0.00% | 0.07% | 3.186M | 3.186M | +0.0018 % |
| homebrew-cask | 0.40% | 0.02% | 7.035M | 7.035M | +0.0065 % |
| homebrew-core | 0.01% | 0.01% | 11.611M | 11.611M | +0.0002 % |
| jdk | 0.26% | 5.64% | 5.537M | 5.540M | +0.0590 % |
| linux | 0.01% | 0.51% | 63.735M | 63.740M | +0.0073 % |
| llvm-project | 0.12% | 0.03% | 25.515M | 25.516M | +0.0050 % |
| rails | 0.10% | 0.10% | 6.252M | 6.252M | +0.0027 % |
| rust | 0.07% | 0.17% | 9.364M | 9.364M | +0.0033 % |
| tensorflow | 0.09% | 1.02% | 7.009M | 7.010M | +0.0158 % |
| webkit | 0.05% | 0.31% | 17.405M | 17.406M | +0.0047 % |
(where the above increase is determined by computing a non-split
commit-graph before and after this patch).
Given that these projects are all "large" by commit count, the storage
cost by writing these filters explicitly is negligible. In the most
extreme example, android-base (which has 494,848 commits at the time of
writing) would have its commit-graph increase by a modest 68.4 KB.
Finally, a test to exercise filters which contain too many changed path
entries will be introduced in a subsequent patch.
Suggested-by: SZEDER Gábor <szeder.dev@gmail.com>
Suggested-by: Jakub Narębski <jnareb@gmail.com>
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Helped-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-18 04:59:44 +02:00
|
|
|
test_filter_trunc_empty () {
|
|
|
|
grep "\"key\":\"filter-trunc-empty\",\"value\":\"$1\"" $2
|
|
|
|
}
|
|
|
|
|
bloom/diff: properly short-circuit on max_changes
Commit e3696980 (diff: halt tree-diff early after max_changes,
2020-03-30) intended to create a mechanism to short-circuit a diff
calculation after a certain number of paths were modified. By
incrementing a "num_changes" counter throughout the recursive
ll_diff_tree_paths(), this was supposed to match the number of changes
that would be written into the changed-path Bloom filters.
Unfortunately, this was not implemented correctly and instead misses
simple cases like file modifications. This then does not stop very
large changed-path filters from being written (unless they add or remove
many files).
To start, change the implementation in ll_diff_tree_paths() to instead
use the global diff_queue_diff struct's 'nr' member as the count. This
is a way to simplify the logic instead of making more mistakes in the
complicated diff code.
This has a drawback: the diff_queue_diff struct only lists the paths
corresponding to blob changes, not their leading directories. Thus,
get_or_compute_bloom_filter() needs an additional check to see if the
hashmap with the leading directories becomes too large.
One reason why this was not caught by test cases was that the test in
t4216-log-bloom.sh that was supposed to check this "too many changes"
condition only checked this on the initial commit of a repository. The
old logic counted these values correctly. Update this test in a few
ways:
1. Use GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS to reduce the limit,
allowing smaller commits to engage with this logic.
2. Create several interesting cases of edits, adds, removes, and mode
changes (in the second commit). By testing both sides of the
inequality with the *_MAX_CHANGED_PATHS variable, we can see that
the count is exactly correct, so none of these changes are missed
or over-counted.
3. Use the trace2 data value filter_found_large to verify that these
commits are on the correct side of the limit.
Another way to verify the behavior is correct is through performance
tests. By testing on my local copies of the Git repository and the Linux
kernel repository, I could measure the effect of these short-circuits
when computing a fresh commit-graph file with changed-path Bloom filters
using the command
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=N time \
git commit-graph write --reachable --changed-paths
and reporting the wall time and resulting commit-graph size.
For Git, the results are
| | N=1 | N=10 | N=512 |
|--------|----------------|----------------|----------------|
| HEAD~1 | 10.90s 9.18MB | 11.11s 9.34MB | 11.31s 9.35MB |
| HEAD | 9.21s 8.62MB | 11.11s 9.29MB | 11.29s 9.34MB |
For Linux, the results are
| | N=1 | N=20 | N=512 |
|--------|----------------|---------------|---------------|
| HEAD~1 | 61.28s 64.3MB | 76.9s 72.6MB | 77.6s 72.6MB |
| HEAD | 49.44s 56.3MB | 68.7s 65.9MB | 69.2s 65.9MB |
Naturally, the improvement becomes much less as the limit grows, as
fewer commits satisfy the short-circuit.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-16 20:07:52 +02:00
|
|
|
test_filter_trunc_large () {
|
|
|
|
grep "\"key\":\"filter-trunc-large\",\"value\":\"$1\"" $2
|
|
|
|
}
|
|
|
|
|
2020-07-01 15:27:23 +02:00
|
|
|
test_expect_success 'correctly report changes over limit' '
|
bloom/diff: properly short-circuit on max_changes
Commit e3696980 (diff: halt tree-diff early after max_changes,
2020-03-30) intended to create a mechanism to short-circuit a diff
calculation after a certain number of paths were modified. By
incrementing a "num_changes" counter throughout the recursive
ll_diff_tree_paths(), this was supposed to match the number of changes
that would be written into the changed-path Bloom filters.
Unfortunately, this was not implemented correctly and instead misses
simple cases like file modifications. This then does not stop very
large changed-path filters from being written (unless they add or remove
many files).
To start, change the implementation in ll_diff_tree_paths() to instead
use the global diff_queue_diff struct's 'nr' member as the count. This
is a way to simplify the logic instead of making more mistakes in the
complicated diff code.
This has a drawback: the diff_queue_diff struct only lists the paths
corresponding to blob changes, not their leading directories. Thus,
get_or_compute_bloom_filter() needs an additional check to see if the
hashmap with the leading directories becomes too large.
One reason why this was not caught by test cases was that the test in
t4216-log-bloom.sh that was supposed to check this "too many changes"
condition only checked this on the initial commit of a repository. The
old logic counted these values correctly. Update this test in a few
ways:
1. Use GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS to reduce the limit,
allowing smaller commits to engage with this logic.
2. Create several interesting cases of edits, adds, removes, and mode
changes (in the second commit). By testing both sides of the
inequality with the *_MAX_CHANGED_PATHS variable, we can see that
the count is exactly correct, so none of these changes are missed
or over-counted.
3. Use the trace2 data value filter_found_large to verify that these
commits are on the correct side of the limit.
Another way to verify the behavior is correct is through performance
tests. By testing on my local copies of the Git repository and the Linux
kernel repository, I could measure the effect of these short-circuits
when computing a fresh commit-graph file with changed-path Bloom filters
using the command
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=N time \
git commit-graph write --reachable --changed-paths
and reporting the wall time and resulting commit-graph size.
For Git, the results are
| | N=1 | N=10 | N=512 |
|--------|----------------|----------------|----------------|
| HEAD~1 | 10.90s 9.18MB | 11.11s 9.34MB | 11.31s 9.35MB |
| HEAD | 9.21s 8.62MB | 11.11s 9.29MB | 11.29s 9.34MB |
For Linux, the results are
| | N=1 | N=20 | N=512 |
|--------|----------------|---------------|---------------|
| HEAD~1 | 61.28s 64.3MB | 76.9s 72.6MB | 77.6s 72.6MB |
| HEAD | 49.44s 56.3MB | 68.7s 65.9MB | 69.2s 65.9MB |
Naturally, the improvement becomes much less as the limit grows, as
fewer commits satisfy the short-circuit.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-16 20:07:52 +02:00
|
|
|
git init limits &&
|
2020-07-01 15:27:23 +02:00
|
|
|
(
|
bloom/diff: properly short-circuit on max_changes
Commit e3696980 (diff: halt tree-diff early after max_changes,
2020-03-30) intended to create a mechanism to short-circuit a diff
calculation after a certain number of paths were modified. By
incrementing a "num_changes" counter throughout the recursive
ll_diff_tree_paths(), this was supposed to match the number of changes
that would be written into the changed-path Bloom filters.
Unfortunately, this was not implemented correctly and instead misses
simple cases like file modifications. This then does not stop very
large changed-path filters from being written (unless they add or remove
many files).
To start, change the implementation in ll_diff_tree_paths() to instead
use the global diff_queue_diff struct's 'nr' member as the count. This
is a way to simplify the logic instead of making more mistakes in the
complicated diff code.
This has a drawback: the diff_queue_diff struct only lists the paths
corresponding to blob changes, not their leading directories. Thus,
get_or_compute_bloom_filter() needs an additional check to see if the
hashmap with the leading directories becomes too large.
One reason why this was not caught by test cases was that the test in
t4216-log-bloom.sh that was supposed to check this "too many changes"
condition only checked this on the initial commit of a repository. The
old logic counted these values correctly. Update this test in a few
ways:
1. Use GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS to reduce the limit,
allowing smaller commits to engage with this logic.
2. Create several interesting cases of edits, adds, removes, and mode
changes (in the second commit). By testing both sides of the
inequality with the *_MAX_CHANGED_PATHS variable, we can see that
the count is exactly correct, so none of these changes are missed
or over-counted.
3. Use the trace2 data value filter_found_large to verify that these
commits are on the correct side of the limit.
Another way to verify the behavior is correct is through performance
tests. By testing on my local copies of the Git repository and the Linux
kernel repository, I could measure the effect of these short-circuits
when computing a fresh commit-graph file with changed-path Bloom filters
using the command
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=N time \
git commit-graph write --reachable --changed-paths
and reporting the wall time and resulting commit-graph size.
For Git, the results are
| | N=1 | N=10 | N=512 |
|--------|----------------|----------------|----------------|
| HEAD~1 | 10.90s 9.18MB | 11.11s 9.34MB | 11.31s 9.35MB |
| HEAD | 9.21s 8.62MB | 11.11s 9.29MB | 11.29s 9.34MB |
For Linux, the results are
| | N=1 | N=20 | N=512 |
|--------|----------------|---------------|---------------|
| HEAD~1 | 61.28s 64.3MB | 76.9s 72.6MB | 77.6s 72.6MB |
| HEAD | 49.44s 56.3MB | 68.7s 65.9MB | 69.2s 65.9MB |
Naturally, the improvement becomes much less as the limit grows, as
fewer commits satisfy the short-circuit.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-16 20:07:52 +02:00
|
|
|
cd limits &&
|
|
|
|
mkdir d &&
|
|
|
|
mkdir d/e &&
|
|
|
|
|
|
|
|
for i in $(test_seq 1 2)
|
2020-07-01 15:27:23 +02:00
|
|
|
do
|
bloom/diff: properly short-circuit on max_changes
Commit e3696980 (diff: halt tree-diff early after max_changes,
2020-03-30) intended to create a mechanism to short-circuit a diff
calculation after a certain number of paths were modified. By
incrementing a "num_changes" counter throughout the recursive
ll_diff_tree_paths(), this was supposed to match the number of changes
that would be written into the changed-path Bloom filters.
Unfortunately, this was not implemented correctly and instead misses
simple cases like file modifications. This then does not stop very
large changed-path filters from being written (unless they add or remove
many files).
To start, change the implementation in ll_diff_tree_paths() to instead
use the global diff_queue_diff struct's 'nr' member as the count. This
is a way to simplify the logic instead of making more mistakes in the
complicated diff code.
This has a drawback: the diff_queue_diff struct only lists the paths
corresponding to blob changes, not their leading directories. Thus,
get_or_compute_bloom_filter() needs an additional check to see if the
hashmap with the leading directories becomes too large.
One reason why this was not caught by test cases was that the test in
t4216-log-bloom.sh that was supposed to check this "too many changes"
condition only checked this on the initial commit of a repository. The
old logic counted these values correctly. Update this test in a few
ways:
1. Use GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS to reduce the limit,
allowing smaller commits to engage with this logic.
2. Create several interesting cases of edits, adds, removes, and mode
changes (in the second commit). By testing both sides of the
inequality with the *_MAX_CHANGED_PATHS variable, we can see that
the count is exactly correct, so none of these changes are missed
or over-counted.
3. Use the trace2 data value filter_found_large to verify that these
commits are on the correct side of the limit.
Another way to verify the behavior is correct is through performance
tests. By testing on my local copies of the Git repository and the Linux
kernel repository, I could measure the effect of these short-circuits
when computing a fresh commit-graph file with changed-path Bloom filters
using the command
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=N time \
git commit-graph write --reachable --changed-paths
and reporting the wall time and resulting commit-graph size.
For Git, the results are
| | N=1 | N=10 | N=512 |
|--------|----------------|----------------|----------------|
| HEAD~1 | 10.90s 9.18MB | 11.11s 9.34MB | 11.31s 9.35MB |
| HEAD | 9.21s 8.62MB | 11.11s 9.29MB | 11.29s 9.34MB |
For Linux, the results are
| | N=1 | N=20 | N=512 |
|--------|----------------|---------------|---------------|
| HEAD~1 | 61.28s 64.3MB | 76.9s 72.6MB | 77.6s 72.6MB |
| HEAD | 49.44s 56.3MB | 68.7s 65.9MB | 69.2s 65.9MB |
Naturally, the improvement becomes much less as the limit grows, as
fewer commits satisfy the short-circuit.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-16 20:07:52 +02:00
|
|
|
printf $i >d/file$i.txt &&
|
|
|
|
printf $i >d/e/file$i.txt || return 1
|
2020-07-01 15:27:23 +02:00
|
|
|
done &&
|
bloom/diff: properly short-circuit on max_changes
Commit e3696980 (diff: halt tree-diff early after max_changes,
2020-03-30) intended to create a mechanism to short-circuit a diff
calculation after a certain number of paths were modified. By
incrementing a "num_changes" counter throughout the recursive
ll_diff_tree_paths(), this was supposed to match the number of changes
that would be written into the changed-path Bloom filters.
Unfortunately, this was not implemented correctly and instead misses
simple cases like file modifications. This then does not stop very
large changed-path filters from being written (unless they add or remove
many files).
To start, change the implementation in ll_diff_tree_paths() to instead
use the global diff_queue_diff struct's 'nr' member as the count. This
is a way to simplify the logic instead of making more mistakes in the
complicated diff code.
This has a drawback: the diff_queue_diff struct only lists the paths
corresponding to blob changes, not their leading directories. Thus,
get_or_compute_bloom_filter() needs an additional check to see if the
hashmap with the leading directories becomes too large.
One reason why this was not caught by test cases was that the test in
t4216-log-bloom.sh that was supposed to check this "too many changes"
condition only checked this on the initial commit of a repository. The
old logic counted these values correctly. Update this test in a few
ways:
1. Use GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS to reduce the limit,
allowing smaller commits to engage with this logic.
2. Create several interesting cases of edits, adds, removes, and mode
changes (in the second commit). By testing both sides of the
inequality with the *_MAX_CHANGED_PATHS variable, we can see that
the count is exactly correct, so none of these changes are missed
or over-counted.
3. Use the trace2 data value filter_found_large to verify that these
commits are on the correct side of the limit.
Another way to verify the behavior is correct is through performance
tests. By testing on my local copies of the Git repository and the Linux
kernel repository, I could measure the effect of these short-circuits
when computing a fresh commit-graph file with changed-path Bloom filters
using the command
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=N time \
git commit-graph write --reachable --changed-paths
and reporting the wall time and resulting commit-graph size.
For Git, the results are
| | N=1 | N=10 | N=512 |
|--------|----------------|----------------|----------------|
| HEAD~1 | 10.90s 9.18MB | 11.11s 9.34MB | 11.31s 9.35MB |
| HEAD | 9.21s 8.62MB | 11.11s 9.29MB | 11.29s 9.34MB |
For Linux, the results are
| | N=1 | N=20 | N=512 |
|--------|----------------|---------------|---------------|
| HEAD~1 | 61.28s 64.3MB | 76.9s 72.6MB | 77.6s 72.6MB |
| HEAD | 49.44s 56.3MB | 68.7s 65.9MB | 69.2s 65.9MB |
Naturally, the improvement becomes much less as the limit grows, as
fewer commits satisfy the short-circuit.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-16 20:07:52 +02:00
|
|
|
|
|
|
|
mkdir mode &&
|
|
|
|
printf bash >mode/script.sh &&
|
|
|
|
|
|
|
|
mkdir foo &&
|
|
|
|
touch foo/bar &&
|
|
|
|
touch foo.txt &&
|
|
|
|
|
|
|
|
git add d foo foo.txt mode &&
|
2020-07-01 15:27:23 +02:00
|
|
|
git commit -m "files" &&
|
bloom/diff: properly short-circuit on max_changes
Commit e3696980 (diff: halt tree-diff early after max_changes,
2020-03-30) intended to create a mechanism to short-circuit a diff
calculation after a certain number of paths were modified. By
incrementing a "num_changes" counter throughout the recursive
ll_diff_tree_paths(), this was supposed to match the number of changes
that would be written into the changed-path Bloom filters.
Unfortunately, this was not implemented correctly and instead misses
simple cases like file modifications. This then does not stop very
large changed-path filters from being written (unless they add or remove
many files).
To start, change the implementation in ll_diff_tree_paths() to instead
use the global diff_queue_diff struct's 'nr' member as the count. This
is a way to simplify the logic instead of making more mistakes in the
complicated diff code.
This has a drawback: the diff_queue_diff struct only lists the paths
corresponding to blob changes, not their leading directories. Thus,
get_or_compute_bloom_filter() needs an additional check to see if the
hashmap with the leading directories becomes too large.
One reason why this was not caught by test cases was that the test in
t4216-log-bloom.sh that was supposed to check this "too many changes"
condition only checked this on the initial commit of a repository. The
old logic counted these values correctly. Update this test in a few
ways:
1. Use GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS to reduce the limit,
allowing smaller commits to engage with this logic.
2. Create several interesting cases of edits, adds, removes, and mode
changes (in the second commit). By testing both sides of the
inequality with the *_MAX_CHANGED_PATHS variable, we can see that
the count is exactly correct, so none of these changes are missed
or over-counted.
3. Use the trace2 data value filter_found_large to verify that these
commits are on the correct side of the limit.
Another way to verify the behavior is correct is through performance
tests. By testing on my local copies of the Git repository and the Linux
kernel repository, I could measure the effect of these short-circuits
when computing a fresh commit-graph file with changed-path Bloom filters
using the command
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=N time \
git commit-graph write --reachable --changed-paths
and reporting the wall time and resulting commit-graph size.
For Git, the results are
| | N=1 | N=10 | N=512 |
|--------|----------------|----------------|----------------|
| HEAD~1 | 10.90s 9.18MB | 11.11s 9.34MB | 11.31s 9.35MB |
| HEAD | 9.21s 8.62MB | 11.11s 9.29MB | 11.29s 9.34MB |
For Linux, the results are
| | N=1 | N=20 | N=512 |
|--------|----------------|---------------|---------------|
| HEAD~1 | 61.28s 64.3MB | 76.9s 72.6MB | 77.6s 72.6MB |
| HEAD | 49.44s 56.3MB | 68.7s 65.9MB | 69.2s 65.9MB |
Naturally, the improvement becomes much less as the limit grows, as
fewer commits satisfy the short-circuit.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-16 20:07:52 +02:00
|
|
|
|
|
|
|
# Commit has 7 file and 4 directory adds
|
|
|
|
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=10 \
|
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace" \
|
|
|
|
git commit-graph write --reachable --changed-paths &&
|
|
|
|
test_max_changed_paths 10 trace &&
|
|
|
|
test_filter_computed 1 trace &&
|
|
|
|
test_filter_trunc_large 1 trace &&
|
|
|
|
|
|
|
|
for path in $(git ls-tree -r --name-only HEAD)
|
|
|
|
do
|
|
|
|
git -c commitGraph.readChangedPaths=false log \
|
|
|
|
-- $path >expect &&
|
|
|
|
git log -- $path >actual &&
|
|
|
|
test_cmp expect actual || return 1
|
|
|
|
done &&
|
|
|
|
|
|
|
|
# Make a variety of path changes
|
|
|
|
printf new1 >d/e/file1.txt &&
|
|
|
|
printf new2 >d/file2.txt &&
|
|
|
|
rm d/e/file2.txt &&
|
|
|
|
rm -r foo &&
|
|
|
|
printf text >foo &&
|
|
|
|
mkdir f &&
|
|
|
|
printf new1 >f/file1.txt &&
|
|
|
|
|
|
|
|
# including a mode-only change (counts as modified)
|
|
|
|
git update-index --chmod=+x mode/script.sh &&
|
|
|
|
|
|
|
|
git add foo d f &&
|
|
|
|
git commit -m "complicated" &&
|
|
|
|
|
|
|
|
# start from scratch and rebuild
|
|
|
|
rm -f .git/objects/info/commit-graph &&
|
|
|
|
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=10 \
|
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace-edit" \
|
|
|
|
git commit-graph write --reachable --changed-paths &&
|
|
|
|
test_max_changed_paths 10 trace-edit &&
|
|
|
|
test_filter_computed 2 trace-edit &&
|
|
|
|
test_filter_trunc_large 2 trace-edit &&
|
|
|
|
|
|
|
|
for path in $(git ls-tree -r --name-only HEAD)
|
|
|
|
do
|
|
|
|
git -c commitGraph.readChangedPaths=false log \
|
|
|
|
-- $path >expect &&
|
|
|
|
git log -- $path >actual &&
|
|
|
|
test_cmp expect actual || return 1
|
|
|
|
done &&
|
|
|
|
|
|
|
|
# start from scratch and rebuild
|
|
|
|
rm -f .git/objects/info/commit-graph &&
|
|
|
|
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=11 \
|
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace-update" \
|
|
|
|
git commit-graph write --reachable --changed-paths &&
|
|
|
|
test_max_changed_paths 11 trace-update &&
|
|
|
|
test_filter_computed 2 trace-update &&
|
|
|
|
test_filter_trunc_large 0 trace-update &&
|
|
|
|
|
|
|
|
for path in $(git ls-tree -r --name-only HEAD)
|
2020-07-01 15:27:23 +02:00
|
|
|
do
|
bloom/diff: properly short-circuit on max_changes
Commit e3696980 (diff: halt tree-diff early after max_changes,
2020-03-30) intended to create a mechanism to short-circuit a diff
calculation after a certain number of paths were modified. By
incrementing a "num_changes" counter throughout the recursive
ll_diff_tree_paths(), this was supposed to match the number of changes
that would be written into the changed-path Bloom filters.
Unfortunately, this was not implemented correctly and instead misses
simple cases like file modifications. This then does not stop very
large changed-path filters from being written (unless they add or remove
many files).
To start, change the implementation in ll_diff_tree_paths() to instead
use the global diff_queue_diff struct's 'nr' member as the count. This
is a way to simplify the logic instead of making more mistakes in the
complicated diff code.
This has a drawback: the diff_queue_diff struct only lists the paths
corresponding to blob changes, not their leading directories. Thus,
get_or_compute_bloom_filter() needs an additional check to see if the
hashmap with the leading directories becomes too large.
One reason why this was not caught by test cases was that the test in
t4216-log-bloom.sh that was supposed to check this "too many changes"
condition only checked this on the initial commit of a repository. The
old logic counted these values correctly. Update this test in a few
ways:
1. Use GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS to reduce the limit,
allowing smaller commits to engage with this logic.
2. Create several interesting cases of edits, adds, removes, and mode
changes (in the second commit). By testing both sides of the
inequality with the *_MAX_CHANGED_PATHS variable, we can see that
the count is exactly correct, so none of these changes are missed
or over-counted.
3. Use the trace2 data value filter_found_large to verify that these
commits are on the correct side of the limit.
Another way to verify the behavior is correct is through performance
tests. By testing on my local copies of the Git repository and the Linux
kernel repository, I could measure the effect of these short-circuits
when computing a fresh commit-graph file with changed-path Bloom filters
using the command
GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS=N time \
git commit-graph write --reachable --changed-paths
and reporting the wall time and resulting commit-graph size.
For Git, the results are
| | N=1 | N=10 | N=512 |
|--------|----------------|----------------|----------------|
| HEAD~1 | 10.90s 9.18MB | 11.11s 9.34MB | 11.31s 9.35MB |
| HEAD | 9.21s 8.62MB | 11.11s 9.29MB | 11.29s 9.34MB |
For Linux, the results are
| | N=1 | N=20 | N=512 |
|--------|----------------|---------------|---------------|
| HEAD~1 | 61.28s 64.3MB | 76.9s 72.6MB | 77.6s 72.6MB |
| HEAD | 49.44s 56.3MB | 68.7s 65.9MB | 69.2s 65.9MB |
Naturally, the improvement becomes much less as the limit grows, as
fewer commits satisfy the short-circuit.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-16 20:07:52 +02:00
|
|
|
git -c commitGraph.readChangedPaths=false log \
|
|
|
|
-- $path >expect &&
|
|
|
|
git log -- $path >actual &&
|
2020-07-01 15:27:23 +02:00
|
|
|
test_cmp expect actual || return 1
|
|
|
|
done
|
|
|
|
)
|
|
|
|
'
|
|
|
|
|
bloom: encode out-of-bounds filters as non-empty
When a changed-path Bloom filter has either zero, or more than a
certain number (commonly 512) of entries, the commit-graph machinery
encodes it as "missing". More specifically, it sets the indices adjacent
in the BIDX chunk as equal to each other to indicate a "length 0"
filter; that is, that the filter occupies zero bytes on disk.
This has heretofore been fine, since the commit-graph machinery has no
need to care about these filters with too few or too many changed paths.
Both cases act like no filter has been generated at all, and so there is
no need to store them.
In a subsequent commit, however, the commit-graph machinery will learn
to only compute Bloom filters for some commits in the current
commit-graph layer. This is a change from the current implementation
which computes Bloom filters for all commits that are in the layer being
written. Critically for this patch, only computing some of the Bloom
filters means adding a third state for length 0 Bloom filters: zero
entries, too many entries, or "hasn't been computed".
It will be important for that future patch to distinguish between "not
representable" (i.e., zero or too-many changed paths), and "hasn't been
computed". In particular, we don't want to waste time recomputing
filters that have already been computed.
To that end, change how we store Bloom filters in the "computed but not
representable" category:
- Bloom filters with no entries are stored as a single byte with all
bits low (i.e., all queries to that Bloom filter will return
"definitely not")
- Bloom filters with too many entries are stored as a single byte with
all bits set high (i.e., all queries to that Bloom filter will
return "maybe").
These rules are sufficient to not incur a behavior change by changing
the on-disk representation of these two classes. Likewise, no
specification changes are necessary for the commit-graph format, either:
- Filters that were previously empty will be recomputed and stored
according to the new rules, and
- old clients reading filters generated by new clients will interpret
the filters correctly and be none the wiser to how they were
generated.
Clients will invoke the Bloom machinery in more cases than before, but
this can be addressed by returning a NULL filter when all bits are set
high. This can be addressed in a future patch.
Note that this does increase the size of on-disk commit-graphs, but far
less than other proposals. In particular, this is generally more
efficient than storing a bitmap for which commits haven't computed their
Bloom filters. Storing a bitmap incurs a penalty of one bit per commit,
whereas storing explicit filters as above incurs a penalty of one byte
per too-large or empty commit.
In practice, these boundary commits likely occupy a small proportion of
the overall number of commits, and so the size penalty is likely smaller
than storing a bitmap for all commits.
See, for example, these relative proportions of such boundary commits
(collected by SZEDER Gábor):
| Percentage of | commit-graph | |
| commits modifying | file size | |
├────────┬──────────────┼───────────────────┤ pct. |
| 0 path | >= 512 paths | before | after | change |
┌────────────────┼────────┼──────────────┼─────────┼─────────┼───────────┤
| android-base | 13.20% | 0.13% | 37.468M | 37.534M | +0.1741 % |
| cmssw | 0.15% | 0.23% | 17.118M | 17.119M | +0.0091 % |
| cpython | 3.07% | 0.01% | 7.967M | 7.971M | +0.0423 % |
| elasticsearch | 0.70% | 1.00% | 8.833M | 8.835M | +0.0128 % |
| gcc | 0.00% | 0.08% | 16.073M | 16.074M | +0.0030 % |
| gecko-dev | 0.14% | 0.64% | 59.868M | 59.874M | +0.0105 % |
| git | 0.11% | 0.02% | 3.895M | 3.895M | +0.0020 % |
| glibc | 0.02% | 0.10% | 3.555M | 3.555M | +0.0021 % |
| go | 0.00% | 0.07% | 3.186M | 3.186M | +0.0018 % |
| homebrew-cask | 0.40% | 0.02% | 7.035M | 7.035M | +0.0065 % |
| homebrew-core | 0.01% | 0.01% | 11.611M | 11.611M | +0.0002 % |
| jdk | 0.26% | 5.64% | 5.537M | 5.540M | +0.0590 % |
| linux | 0.01% | 0.51% | 63.735M | 63.740M | +0.0073 % |
| llvm-project | 0.12% | 0.03% | 25.515M | 25.516M | +0.0050 % |
| rails | 0.10% | 0.10% | 6.252M | 6.252M | +0.0027 % |
| rust | 0.07% | 0.17% | 9.364M | 9.364M | +0.0033 % |
| tensorflow | 0.09% | 1.02% | 7.009M | 7.010M | +0.0158 % |
| webkit | 0.05% | 0.31% | 17.405M | 17.406M | +0.0047 % |
(where the above increase is determined by computing a non-split
commit-graph before and after this patch).
Given that these projects are all "large" by commit count, the storage
cost by writing these filters explicitly is negligible. In the most
extreme example, android-base (which has 494,848 commits at the time of
writing) would have its commit-graph increase by a modest 68.4 KB.
Finally, a test to exercise filters which contain too many changed path
entries will be introduced in a subsequent patch.
Suggested-by: SZEDER Gábor <szeder.dev@gmail.com>
Suggested-by: Jakub Narębski <jnareb@gmail.com>
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Helped-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-18 04:59:44 +02:00
|
|
|
test_expect_success 'correctly report commits with no changed paths' '
|
|
|
|
git init empty &&
|
|
|
|
test_when_finished "rm -fr empty" &&
|
|
|
|
(
|
|
|
|
cd empty &&
|
|
|
|
|
|
|
|
git commit --allow-empty -m "initial commit" &&
|
|
|
|
|
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace.event" \
|
|
|
|
git commit-graph write --reachable --changed-paths &&
|
|
|
|
test_filter_computed 1 trace.event &&
|
|
|
|
test_filter_not_computed 0 trace.event &&
|
|
|
|
test_filter_trunc_empty 1 trace.event &&
|
|
|
|
test_filter_trunc_large 0 trace.event
|
|
|
|
)
|
|
|
|
'
|
|
|
|
|
2020-09-18 15:27:27 +02:00
|
|
|
test_expect_success 'Bloom generation is limited by --max-new-filters' '
|
|
|
|
(
|
|
|
|
cd limits &&
|
|
|
|
test_commit c2 filter &&
|
|
|
|
test_commit c3 filter &&
|
|
|
|
test_commit c4 no-filter &&
|
|
|
|
|
|
|
|
rm -f trace.event &&
|
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace.event" \
|
|
|
|
git commit-graph write --reachable --split=replace \
|
|
|
|
--changed-paths --max-new-filters=2 &&
|
|
|
|
|
|
|
|
test_filter_computed 2 trace.event &&
|
|
|
|
test_filter_not_computed 3 trace.event &&
|
|
|
|
test_filter_trunc_empty 0 trace.event &&
|
|
|
|
test_filter_trunc_large 0 trace.event
|
|
|
|
)
|
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success 'Bloom generation backfills previously-skipped filters' '
|
2020-09-18 04:59:57 +02:00
|
|
|
# Check specifying commitGraph.maxNewFilters over "git config" works.
|
|
|
|
test_config -C limits commitGraph.maxNewFilters 1 &&
|
2020-09-18 15:27:27 +02:00
|
|
|
(
|
|
|
|
cd limits &&
|
|
|
|
|
|
|
|
rm -f trace.event &&
|
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace.event" \
|
|
|
|
git commit-graph write --reachable --changed-paths \
|
2020-09-18 04:59:57 +02:00
|
|
|
--split=replace &&
|
2020-09-18 15:27:27 +02:00
|
|
|
test_filter_computed 1 trace.event &&
|
|
|
|
test_filter_not_computed 4 trace.event &&
|
|
|
|
test_filter_trunc_empty 0 trace.event &&
|
|
|
|
test_filter_trunc_large 0 trace.event
|
|
|
|
)
|
|
|
|
'
|
|
|
|
|
2020-09-18 04:59:57 +02:00
|
|
|
test_expect_success '--max-new-filters overrides configuration' '
|
|
|
|
git init override &&
|
|
|
|
test_when_finished "rm -fr override" &&
|
|
|
|
test_config -C override commitGraph.maxNewFilters 2 &&
|
|
|
|
(
|
|
|
|
cd override &&
|
|
|
|
test_commit one &&
|
|
|
|
test_commit two &&
|
|
|
|
|
|
|
|
rm -f trace.event &&
|
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace.event" \
|
|
|
|
git commit-graph write --reachable --changed-paths \
|
|
|
|
--max-new-filters=1 &&
|
|
|
|
test_filter_computed 1 trace.event &&
|
|
|
|
test_filter_not_computed 1 trace.event &&
|
|
|
|
test_filter_trunc_empty 0 trace.event &&
|
|
|
|
test_filter_trunc_large 0 trace.event
|
|
|
|
)
|
|
|
|
'
|
|
|
|
|
2020-09-18 15:27:27 +02:00
|
|
|
test_expect_success 'Bloom generation backfills empty commits' '
|
|
|
|
git init empty &&
|
|
|
|
test_when_finished "rm -fr empty" &&
|
|
|
|
(
|
|
|
|
cd empty &&
|
|
|
|
for i in $(test_seq 1 6)
|
|
|
|
do
|
|
|
|
git commit --allow-empty -m "$i"
|
|
|
|
done &&
|
|
|
|
|
|
|
|
# Generate Bloom filters for empty commits 1-6, two at a time.
|
|
|
|
for i in $(test_seq 1 3)
|
|
|
|
do
|
|
|
|
rm -f trace.event &&
|
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace.event" \
|
|
|
|
git commit-graph write --reachable \
|
|
|
|
--changed-paths --max-new-filters=2 &&
|
|
|
|
test_filter_computed 2 trace.event &&
|
|
|
|
test_filter_not_computed 4 trace.event &&
|
|
|
|
test_filter_trunc_empty 2 trace.event &&
|
|
|
|
test_filter_trunc_large 0 trace.event
|
|
|
|
done &&
|
|
|
|
|
|
|
|
# Finally, make sure that once all commits have filters, that
|
|
|
|
# none are subsequently recomputed.
|
|
|
|
rm -f trace.event &&
|
|
|
|
GIT_TRACE2_EVENT="$(pwd)/trace.event" \
|
|
|
|
git commit-graph write --reachable \
|
|
|
|
--changed-paths --max-new-filters=2 &&
|
|
|
|
test_filter_computed 0 trace.event &&
|
|
|
|
test_filter_not_computed 6 trace.event &&
|
|
|
|
test_filter_trunc_empty 0 trace.event &&
|
|
|
|
test_filter_trunc_large 0 trace.event
|
|
|
|
)
|
|
|
|
'
|
|
|
|
|
2020-05-08 01:51:02 +02:00
|
|
|
test_done
|