@matheusbsbs / matheus-bagliano / commits / 43f70eaea0

refs/reftable: precompute prefix length

We're recomputing the prefix length on every iteration of the ref iterator. Precompute it for another speedup when iterating over 1 million refs: Benchmark 1: show-ref: single matching ref (revision = HEAD~) Time (mean ± σ): 100.3 ms ± 3.7 ms [User: 97.3 ms, System: 2.8 ms] Range (min … max): 97.5 ms … 139.7 ms 1000 runs Benchmark 2: show-ref: single matching ref (revision = HEAD) Time (mean ± σ): 95.8 ms ± 3.4 ms [User: 92.9 ms, System: 2.8 ms] Range (min … max): 93.0 ms … 121.9 ms 1000 runs Summary show-ref: single matching ref (revision = HEAD) ran 1.05 ± 0.05 times faster than show-ref: single matching ref (revision = HEAD~) Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Patrick Steinhardt committed Mar 4, 2024 at 11:49 UTC 43f70eaea0e3fa9d98c895e9341674a67262b657

1 file changed +4 -2

refs/reftable-backend.c

+4 -2

@@ -346,6 +346,7 @@ struct reftable_ref_iterator {

346 struct object_id oid;

347

348 const char *prefix;

349 + size_t prefix_len;

350 unsigned int flags;

351 int err;

352 };

@@ -371,8 +372,8 @@ static int reftable_ref_iterator_advance(struct ref_iterator *ref_iterator)

372 if (!starts_with(iter->ref.refname, "refs/"))

373 continue;

374

374 - if (iter->prefix &&

375 - strncmp(iter->prefix, iter->ref.refname, strlen(iter->prefix))) {

375 + if (iter->prefix_len &&

376 + strncmp(iter->prefix, iter->ref.refname, iter->prefix_len)) {

377 iter->err = 1;

378 break;

379 }

@@ -481,6 +482,7 @@ static struct reftable_ref_iterator *ref_iterator_for_stack(struct reftable_ref_

482 iter = xcalloc(1, sizeof(*iter));

483 base_ref_iterator_init(&iter->base, &reftable_ref_iterator_vtable, 1);

484 iter->prefix = prefix;

485 + iter->prefix_len = prefix ? strlen(prefix) : 0;

486 iter->base.oid = &iter->oid;

487 iter->flags = flags;

488 iter->refs = refs;