From 00bd6c3e4649d3e764db7ffcfbd317aabd2525d3 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Wed, 20 Nov 2024 08:51:34 +0100 Subject: [PATCH] refs: use "initial" transaction semantics to migrate refs MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Until now, we couldn't use "initial" transaction semantics to migrate refs because the "files" backend only supported writing regular refs via the initial transaction because it simply mapped the transaction to a "packed-refs" transaction. But with the preceding commit, the "files" backend has learned to also write symbolic and root refs in the initial transaction by creating a second transaction for all refs that need to be written as loose refs. Adapt the code to migrate refs to commit the transaction as an initial transaction. This results in a signiticant speedup when migrating many refs: Benchmark 1: migrate reftable:files (refcount = 100000, revision = HEAD~) Time (mean ± σ): 3.247 s ± 0.034 s [User: 0.485 s, System: 2.722 s] Range (min … max): 3.216 s … 3.309 s 10 runs Benchmark 2: migrate reftable:files (refcount = 100000, revision = HEAD) Time (mean ± σ): 453.6 ms ± 1.9 ms [User: 214.6 ms, System: 230.5 ms] Range (min … max): 451.5 ms … 456.4 ms 10 runs Summary migrate reftable:files (refcount = 100000, revision = HEAD) ran 7.16 ± 0.08 times faster than migrate reftable:files (refcount = 100000, revision = HEAD~) As the reftable backend doesn't (yet) special-case initial transactions there is no comparable speedup for that backend. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- refs.c | 10 ++-------- t/t1460-refs-migrate.sh | 2 +- 2 files changed, 3 insertions(+), 9 deletions(-) diff --git a/refs.c b/refs.c index 8b9dfc6173..0f10c565bb 100644 --- a/refs.c +++ b/refs.c @@ -2827,7 +2827,8 @@ int repo_migrate_ref_storage_format(struct repository *repo, if (ret < 0) goto done; - transaction = ref_store_transaction_begin(new_refs, 0, errbuf); + transaction = ref_store_transaction_begin(new_refs, REF_TRANSACTION_FLAG_INITIAL, + errbuf); if (!transaction) goto done; @@ -2852,13 +2853,6 @@ int repo_migrate_ref_storage_format(struct repository *repo, if (ret < 0) goto done; - /* - * TODO: we might want to migrate to `initial_ref_transaction_commit()` - * here, which is more efficient for the files backend because it would - * write new refs into the packed-refs file directly. At this point, - * the files backend doesn't handle pseudo-refs and symrefs correctly - * though, so this requires some more work. - */ ret = ref_transaction_commit(transaction, errbuf); if (ret < 0) goto done; diff --git a/t/t1460-refs-migrate.sh b/t/t1460-refs-migrate.sh index f7c0783d30..b90b38a87f 100755 --- a/t/t1460-refs-migrate.sh +++ b/t/t1460-refs-migrate.sh @@ -237,7 +237,7 @@ test_expect_success 'migrating from reftable format deletes backend files' ' test_path_is_missing repo/.git/reftable && echo "ref: refs/heads/main" >expect && test_cmp expect repo/.git/HEAD && - test_path_is_file repo/.git/refs/heads/main + test_path_is_file repo/.git/packed-refs ' test_done -- 2.39.5