[PATCH V1][RFC] t/perf/p3400: speed up setup using fast-import
- From
Tian Yuchen <a3205153416@gmail.com>
- Date
- Jan 26, 2026, 16:56 UTC
- Message-ID
- <20260126165618.596944-1-a3205153416@gmail.com>
The setup phase in 't/perf/p3400-rebase.sh' generates 100 commits to simulate a noisy history. It currently uses a shell loop that invokes 'git add', 'git commit', 'test_seq', and 'sort' in each iteration. This makes the whole process slow.
Optimize the setup by using 'git fast-import' to generate the commit history in a single stream. Additionally, pre-compute the forward and reversed file contents to avoid repetitive execution of 'seq' and 'sort'.
Performance enhancement: Before: 29.045s After: 18.081s
Measured on Lenovo Yoga 2020, Ubuntu 24.04.
Signed-off-by: Tian Yuchen <a3205153416@gmail.com> --- t/perf/p3400-rebase.sh | 53 +++++++++++++++++++++++++++++------------- 1 file changed, 37 insertions(+), 16 deletions(-)
diff --git a/t/perf/p3400-rebase.sh b/t/perf/p3400-rebase.sh index e6b0277729..9251a09b4f 100755 --- a/t/perf/p3400-rebase.sh +++ b/t/perf/p3400-rebase.sh @@ -9,25 +9,46 @@ test_expect_success 'setup rebasing on top of a lot of changes' ' git checkout -f -B base && git checkout -B to-rebase && git checkout -B upstream && - for i in $(test_seq 100) - do - # simulate huge diffs - echo change$i >unrelated-file$i && - test_seq 1000 >>unrelated-file$i && - git add unrelated-file$i && - test_tick && - git commit -m commit$i unrelated-file$i && - echo change$i >unrelated-file$i && - test_seq 1000 | sort -nr >>unrelated-file$i && - git add unrelated-file$i && - test_tick && - git commit -m commit$i-reverse unrelated-file$i || - return 1 - done && + + test_seq 1000 >content_fwd && + test_seq 1000 | sort -nr >content_rev && + + ( + for i in $(test_seq 100) + do + echo "commit refs/heads/upstream" && + echo "committer WGYDY <author@mock.com> $i +0000" && + echo "data <<EOF" && + echo "commit$i" && + echo "EOF" && + + if test "$i" = 1; then + echo "from refs/heads/upstream^0" + fi && + + echo "M 100644 inline unrelated-file$i" && + echo "data <<EOF" && + echo "change$i" && + cat content_fwd && + echo "EOF" && + + echo "commit refs/heads/upstream" && + echo "committer WGYDY <author@mock.com> $i +0000" && + echo "data <<EOF" && + echo "commit$i-reversed" && + echo "EOF" && + echo "M 100644 inline unrelated-file$i" && + echo "data <<EOF" && + echo "change$i" && + cat content_rev && + echo "EOF" || return 1 + done + ) | git fast-import && + + git checkout -f upstream && git checkout to-rebase && test_commit our-patch interesting-file ' - test_perf 'rebase on top of a lot of unrelated changes' ' git rebase --onto upstream HEAD^ && git rebase --onto base HEAD^
-- 2.43.0