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Merge branch 'rs/merge-base-optim' 

The code to walk revision graph to compute merge base has been
optimized.

* rs/merge-base-optim:
  commit-reach: avoid commit_list_insert_by_date()
main
Junio C Hamano 2025-11-03 06:49:55 -08:00
parent 249b0d3f03 134ec330d2
commit a4b1a1478b
2 changed files with 110 additions and 5 deletions
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14
commit-reach.c
View File

@ -60,6 +60,7 @@ static int paint_down_to_common(struct repository *r,
struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
int i;
timestamp_t last_gen = GENERATION_NUMBER_INFINITY;
struct commit_list **tail = result;

if (!min_generation && !corrected_commit_dates_enabled(r))
queue.compare = compare_commits_by_commit_date;
@ -95,7 +96,7 @@ static int paint_down_to_common(struct repository *r,
if (flags == (PARENT1 | PARENT2)) {
if (!(commit->object.flags & RESULT)) {
commit->object.flags |= RESULT;
commit_list_insert_by_date(commit, result);
tail = commit_list_append(commit, tail);
}
/* Mark parents of a found merge stale */
flags |= STALE;
@ -128,6 +129,7 @@ static int paint_down_to_common(struct repository *r,
}

clear_prio_queue(&queue);
commit_list_sort_by_date(result);
return 0;
}

@ -136,7 +138,7 @@ static int merge_bases_many(struct repository *r,
struct commit **twos,
struct commit_list **result)
{
struct commit_list *list = NULL;
struct commit_list *list = NULL, **tail = result;
int i;

for (i = 0; i < n; i++) {
@ -171,8 +173,9 @@ static int merge_bases_many(struct repository *r,
while (list) {
struct commit *commit = pop_commit(&list);
if (!(commit->object.flags & STALE))
commit_list_insert_by_date(commit, result);
tail = commit_list_append(commit, tail);
}
commit_list_sort_by_date(result);
return 0;
}

@ -425,7 +428,7 @@ static int get_merge_bases_many_0(struct repository *r,
int cleanup,
struct commit_list **result)
{
struct commit_list *list;
struct commit_list *list, **tail = result;
struct commit **rslt;
size_t cnt, i;
int ret;
@ -461,7 +464,8 @@ static int get_merge_bases_many_0(struct repository *r,
return -1;
}
for (i = 0; i < cnt; i++)
commit_list_insert_by_date(rslt[i], result);
tail = commit_list_append(rslt[i], tail);
commit_list_sort_by_date(result);
free(rslt);
return 0;
}

101
t/perf/p6010-merge-base.sh Executable file
View File

@ -0,0 +1,101 @@
#!/bin/sh

test_description='Test git merge-base'

. ./perf-lib.sh

test_perf_fresh_repo

#
# Creates lots of merges to make history traversal costly. In
# particular it creates 2^($max_level-1)-1 2-way merges on top of
# 2^($max_level-1) root commits. E.g., the commit history looks like
# this for a $max_level of 3:
#
# _1_
# / \
# 2 3
# / \ / \
# 4 5 6 7
#
# The numbers are the fast-import marks, which also are the commit
# messages. 1 is the HEAD commit and a merge, 2 and 3 are also merges,
# 4-7 are the root commits.
#
build_history () {
local max_level="$1" &&
local level="${2:-1}" &&
local mark="${3:-1}" &&
if test $level -eq $max_level
then
echo "reset refs/heads/master" &&
echo "from $ZERO_OID" &&
echo "commit refs/heads/master" &&
echo "mark :$mark" &&
echo "committer C <c@example.com> 1234567890 +0000" &&
echo "data <<EOF" &&
echo "$mark" &&
echo "EOF"
else
local level1=$((level+1)) &&
local mark1=$((2*mark)) &&
local mark2=$((2*mark+1)) &&
build_history $max_level $level1 $mark1 &&
build_history $max_level $level1 $mark2 &&
echo "commit refs/heads/master" &&
echo "mark :$mark" &&
echo "committer C <c@example.com> 1234567890 +0000" &&
echo "data <<EOF" &&
echo "$mark" &&
echo "EOF" &&
echo "from :$mark1" &&
echo "merge :$mark2"
fi
}

#
# Creates a new merge history in the same shape as build_history does,
# while reusing the same root commits. This way the two top commits
# have 2^($max_level-1) merge bases between them.
#
build_history2 () {
local max_level="$1" &&
local level="${2:-1}" &&
local mark="${3:-1}" &&
if test $level -lt $max_level
then
local level1=$((level+1)) &&
local mark1=$((2*mark)) &&
local mark2=$((2*mark+1)) &&
build_history2 $max_level $level1 $mark1 &&
build_history2 $max_level $level1 $mark2 &&
echo "commit refs/heads/master" &&
echo "mark :$mark" &&
echo "committer C <c@example.com> 1234567890 +0000" &&
echo "data <<EOF" &&
echo "$mark II" &&
echo "EOF" &&
echo "from :$mark1" &&
echo "merge :$mark2"
fi
}

test_expect_success 'setup' '
max_level=15 &&
build_history $max_level | git fast-import --export-marks=marks &&
git tag one &&
build_history2 $max_level | git fast-import --import-marks=marks --force &&
git tag two &&
git gc &&
git log --format=%H --no-merges >expect
'

test_perf 'git merge-base' '
git merge-base --all one two >actual
'

test_expect_success 'verify result' '
test_cmp expect actual
'

test_done