git/t/perf/p1500-graph-walks.sh

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for-each-ref: add ahead-behind format atom The previous change implemented the ahead_behind() method, including an algorithm to compute the ahead/behind values for a number of commit tips relative to a number of commit bases. Now, integrate that algorithm as part of 'git for-each-ref' hidden behind a new format atom, ahead-behind. This naturally extends to 'git branch' and 'git tag' builtins, as well. This format allows specifying multiple bases, if so desired, and all matching references are compared against all of those bases. For this reason, failing to read a reference provided from these atoms results in an error. In order to translate the ahead_behind() method information to the format output code in ref-filter.c, we must populate arrays of ahead_behind_count structs. In struct ref_array, we store the full array that will be passed to ahead_behind(). In struct ref_array_item, we store an array of pointers that point to the relvant items within the full array. In this way, we can pull all relevant ahead/behind values directly when formatting output for a specific item. It also ensures the lifetime of the ahead_behind_count structs matches the time that the array is being used. Add specific tests of the ahead/behind counts in t6600-test-reach.sh, as it has an interesting repository shape. In particular, its merging strategy and its use of different commit-graphs would demonstrate over- counting if the ahead_behind() method did not already account for that possibility. Also add tests for the specific for-each-ref, branch, and tag builtins. In the case of 'git tag', there are intersting cases that happen when some of the selected tips are not commits. This requires careful logic around commits_nr in the second loop of filter_ahead_behind(). Also, the test in t7004 is carefully located to avoid being dependent on the GPG prereq. It also avoids using the test_commit helper, as that will add ticks to the time and disrupt the expected timestamps in later tag tests. Also add performance tests in a new p1300-graph-walks.sh script. This will be useful for more uses in the future, but for now compare the ahead-behind counting algorithm in 'git for-each-ref' to the naive implementation by running 'git rev-list --count' processes for each input. For the Git source code repository, the improvement is already obvious: Test this tree --------------------------------------------------------------- 1500.2: ahead-behind counts: git for-each-ref 0.07(0.07+0.00) 1500.3: ahead-behind counts: git branch 0.07(0.06+0.00) 1500.4: ahead-behind counts: git tag 0.07(0.06+0.00) 1500.5: ahead-behind counts: git rev-list 1.32(1.04+0.27) But the standard performance benchmark is the Linux kernel repository, which demosntrates a significant improvement: Test this tree --------------------------------------------------------------- 1500.2: ahead-behind counts: git for-each-ref 0.27(0.24+0.02) 1500.3: ahead-behind counts: git branch 0.27(0.24+0.03) 1500.4: ahead-behind counts: git tag 0.28(0.27+0.01) 1500.5: ahead-behind counts: git rev-list 4.57(4.03+0.54) The 'git rev-list' test exists in this change as a demonstration, but it will be removed in the next change to avoid wasting time on this comparison. Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-20 11:26:54 +00:00
#!/bin/sh
test_description='Commit walk performance tests'
. ./perf-lib.sh
test_perf_large_repo
test_expect_success 'setup' '
git for-each-ref --format="%(refname)" "refs/heads/*" "refs/tags/*" >allrefs &&
sort -r allrefs | head -n 50 >refs &&
for ref in $(cat refs)
do
git branch -f ref-$ref $ref &&
echo ref-$ref ||
return 1
done >branches &&
for ref in $(cat refs)
do
git tag -f tag-$ref $ref &&
echo tag-$ref ||
return 1
done >tags &&
git commit-graph write --reachable
'
test_perf 'ahead-behind counts: git for-each-ref' '
git for-each-ref --format="%(ahead-behind:HEAD)" --stdin <refs
'
test_perf 'ahead-behind counts: git branch' '
xargs git branch -l --format="%(ahead-behind:HEAD)" <branches
'
test_perf 'ahead-behind counts: git tag' '
xargs git tag -l --format="%(ahead-behind:HEAD)" <tags
'
commit-reach: add tips_reachable_from_bases() Both 'git for-each-ref --merged=<X>' and 'git branch --merged=<X>' use the ref-filter machinery to select references or branches (respectively) that are reachable from a set of commits presented by one or more --merged arguments. This happens within reach_filter(), which uses the revision-walk machinery to walk history in a standard way. However, the commit-reach.c file is full of custom searches that are more efficient, especially for reachability queries that can terminate early when reachability is discovered. Add a new tips_reachable_from_bases() method to commit-reach.c and call it from within reach_filter() in ref-filter.c. This affects both 'git branch' and 'git for-each-ref' as tested in p1500-graph-walks.sh. For the Linux kernel repository, we take an already-fast algorithm and make it even faster: Test HEAD~1 HEAD ------------------------------------------------------------------- 1500.5: contains: git for-each-ref --merged 0.13 0.02 -84.6% 1500.6: contains: git branch --merged 0.14 0.02 -85.7% 1500.7: contains: git tag --merged 0.15 0.03 -80.0% (Note that we remove the iterative 'git rev-list' test from p1500 because it no longer makes sense as a comparison to 'git for-each-ref' and would just waste time running it for these comparisons.) The algorithm is implemented in commit-reach.c in the method tips_reachable_from_base(). This method takes a string_list of tips and assigns the 'util' for each item with the value 1 if the base commit can reach those tips. Like other reachability queries in commit-reach.c, the fastest way to search for "can A reach B?" is to do a depth-first search up to the generation number of B, preferring to explore first parents before later parents. While we must walk all reachable commits up to that generation number when the answer is "no", the depth-first search can answer "yes" much faster than other approaches in most cases. This search becomes trickier when there are multiple targets for the depth-first search. The commits with lower generation number are more likely to be within the history of the start commit, but we don't want to waste time searching commits of low generation number if the commit target with lowest generation number has already been found. The trick here is to take the input commits and sort them by generation number in ascending order. Track the index within this order as min_generation_index. When we find a commit, if its index in the list is equal to min_generation_index, then we can increase the generation number boundary of our search to the next-lowest value in the list. With this mechanism, the number of commits to search is minimized with respect to the depth-first search heuristic. We will walk all commits up to the minimum generation number of a commit that is _not_ reachable from the start, but we will walk only the necessary portion of the depth-first search for the reachable commits of lower generation. Add extra tests for this behavior in t6600-test-reach.sh as the interesting data shape of that repository can sometimes demonstrate corner case bugs. Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-20 11:26:55 +00:00
test_perf 'contains: git for-each-ref --merged' '
git for-each-ref --merged=HEAD --stdin <refs
'
test_perf 'contains: git branch --merged' '
xargs git branch --merged=HEAD <branches
'
test_perf 'contains: git tag --merged' '
xargs git tag --merged=HEAD <tags
for-each-ref: add ahead-behind format atom The previous change implemented the ahead_behind() method, including an algorithm to compute the ahead/behind values for a number of commit tips relative to a number of commit bases. Now, integrate that algorithm as part of 'git for-each-ref' hidden behind a new format atom, ahead-behind. This naturally extends to 'git branch' and 'git tag' builtins, as well. This format allows specifying multiple bases, if so desired, and all matching references are compared against all of those bases. For this reason, failing to read a reference provided from these atoms results in an error. In order to translate the ahead_behind() method information to the format output code in ref-filter.c, we must populate arrays of ahead_behind_count structs. In struct ref_array, we store the full array that will be passed to ahead_behind(). In struct ref_array_item, we store an array of pointers that point to the relvant items within the full array. In this way, we can pull all relevant ahead/behind values directly when formatting output for a specific item. It also ensures the lifetime of the ahead_behind_count structs matches the time that the array is being used. Add specific tests of the ahead/behind counts in t6600-test-reach.sh, as it has an interesting repository shape. In particular, its merging strategy and its use of different commit-graphs would demonstrate over- counting if the ahead_behind() method did not already account for that possibility. Also add tests for the specific for-each-ref, branch, and tag builtins. In the case of 'git tag', there are intersting cases that happen when some of the selected tips are not commits. This requires careful logic around commits_nr in the second loop of filter_ahead_behind(). Also, the test in t7004 is carefully located to avoid being dependent on the GPG prereq. It also avoids using the test_commit helper, as that will add ticks to the time and disrupt the expected timestamps in later tag tests. Also add performance tests in a new p1300-graph-walks.sh script. This will be useful for more uses in the future, but for now compare the ahead-behind counting algorithm in 'git for-each-ref' to the naive implementation by running 'git rev-list --count' processes for each input. For the Git source code repository, the improvement is already obvious: Test this tree --------------------------------------------------------------- 1500.2: ahead-behind counts: git for-each-ref 0.07(0.07+0.00) 1500.3: ahead-behind counts: git branch 0.07(0.06+0.00) 1500.4: ahead-behind counts: git tag 0.07(0.06+0.00) 1500.5: ahead-behind counts: git rev-list 1.32(1.04+0.27) But the standard performance benchmark is the Linux kernel repository, which demosntrates a significant improvement: Test this tree --------------------------------------------------------------- 1500.2: ahead-behind counts: git for-each-ref 0.27(0.24+0.02) 1500.3: ahead-behind counts: git branch 0.27(0.24+0.03) 1500.4: ahead-behind counts: git tag 0.28(0.27+0.01) 1500.5: ahead-behind counts: git rev-list 4.57(4.03+0.54) The 'git rev-list' test exists in this change as a demonstration, but it will be removed in the next change to avoid wasting time on this comparison. Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-20 11:26:54 +00:00
'
test_done