[PATCH on sb/more-repo-in-api] revision: use commit graph in get_reference()
- From
- Jonathan Tan <jonathantanmy@google.com>
- Date
- Dec 4, 2018, 22:42 UTC
- Message-ID
- <20181204224238.50966-1-jonathantanmy@google.com>
When fetching into a repository, a connectivity check is first made by check_exist_and_connected() in builtin/fetch.c that runs:
git rev-list --objects --stdin --not --all --quiet <(list of objects)
If the client repository has many refs, this command can be slow, regardless of the nature of the server repository or what is being fetched. A profiler reveals that most of the time is spent in setup_revisions() (approx. 60/63), and of the time spent in setup_revisions(), most of it is spent in parse_object() (approx. 49/60). This is because setup_revisions() parses the target of every ref (from "--all"), and parse_object() reads the buffer of the object.
Reading the buffer is unnecessary if the repository has a commit graph and if the ref points to a commit (which is typically the case). This patch uses the commit graph wherever possible; on my computer, when I run the above command with a list of 1 object on a many-ref repository, I get a speedup from 1.8s to 1.0s.
Another way to accomplish this effect would be to modify parse_object() to use the commit graph if possible; however, I did not want to change parse_object()'s current behavior of always checking the object signature of the returned object.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com> --- This is on sb/more-repo-in-api because I'm using the repo_parse_commit() function.
A colleague noticed this issue when handling a mirror clone.
Looking at the bigger picture, the speed of the connectivity check during a fetch might be further improved by passing only the negotiation tips (obtained through --negotiation-tip) instead of "--all". This patch just handles the low-hanging fruit first. --- revision.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/revision.c b/revision.c index b5108b75ab..e7da2c57ab 100644 --- a/revision.c +++ b/revision.c @@ -212,7 +212,20 @@ static struct object *get_reference(struct rev_info *revs, const char *name, { struct object *object; - object = parse_object(revs->repo, oid); + /* + * If the repository has commit graphs, repo_parse_commit() avoids + * reading the object buffer, so use it whenever possible. + */ + if (oid_object_info(revs->repo, oid, NULL) == OBJ_COMMIT) { + struct commit *c = lookup_commit(revs->repo, oid); + if (!repo_parse_commit(revs->repo, c)) + object = (struct object *) c; + else + object = NULL; + } else { + object = parse_object(revs->repo, oid); + } + if (!object) { if (revs->ignore_missing) return object;
-- 2.19.0.271.gfe8321ec05.dirty