dilim/git
1
0
Fork 0
mirror of https://github.com/git/git.git synced 2026-08-05 23:51:27 +00:00
Code Issues Packages Projects Releases Wiki Activity

commit-graph: add trace2 instrumentation for generation DFS

Browse Source 
Count the number of steps taken in
compute_reachable_generation_numbers() and expose it via
trace2 to make it easier to detect performance regressions.

Add a failing test for such a regression, introduced in
199d452758 (commit-graph: return the prepared commit graph
from `prepare_commit_graph()`, 2025-09-04), where incremental
commit-graph writes do not see existing generation numbers
from lower graph layers and fall back to walking the full
ancestry.

Signed-off-by: Kristofer Karlsson <krka@spotify.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Kristofer Karlsson
2026-07-09 15:03:00 +00:00
committed by Junio C Hamano
parent f85a7e6620
commit 02d62c33be
2 changed files with 29 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
commit-graph.c
View File

@@ -1653,6 +1653,7 @@ static void compute_reachable_generation_numbers(
{
int i;
struct commit_list *list = NULL;
intmax_t steps = 0;
for (i = 0; i < info->commits->nr; i++) {
struct commit *c = info->commits->items[i];
@@ -1671,6 +1672,7 @@ static void compute_reachable_generation_numbers(
int all_parents_computed = 1;
timestamp_t max_gen = 0;
steps++;
for (parent = current->parents; parent; parent = parent->next) {
repo_parse_commit(info->r, parent->item);
gen = info->get_generation(parent->item, info->data);
@@ -1694,6 +1696,9 @@ static void compute_reachable_generation_numbers(
}
}
}
trace2_data_intmax("commit-graph", info->r,
"generation-dfs-steps", steps);
}
static timestamp_t get_topo_level(struct commit *c, void *data)

24
t/t5324-split-commit-graph.sh
View File

@@ -718,6 +718,30 @@ test_expect_success 'write generation data chunk when commit-graph chain is repl
)
'
test_expect_failure 'incremental write reads topo levels from all layers' '
git init topo-from-lower &&
(
cd topo-from-lower &&
for i in $(test_seq 5)
do
test_commit base-$i || return 1
done &&
git commit-graph write --reachable &&
test_commit extra &&
git commit-graph write --reachable --split=no-merge &&
git checkout base-3 &&
test_commit new-branch &&
GIT_TRACE2_EVENT="$(pwd)/trace.txt" \
git commit-graph write --reachable --split=no-merge &&
test_trace2_data commit-graph generation-dfs-steps 1 <trace.txt
)
'
test_expect_success 'temporary graph layer is discarded upon failure' '
git init layer-discard &&
(