On Tue, Mar 01, 2022 at 09:43:19AM +0100, Patrick Steinhardt wrote:
> On Wed, Feb 23, 2022 at 09:13:53AM -0500, Derrick Stolee wrote:
> > On 2/23/2022 7:35 AM, Patrick Steinhardt wrote:
> >
> > > The following benchmark is executed in a repository with a huge number
> > > of references. It uses cached request from git-fetch(1) as input and
> > > contains about 876,000 "want" lines:
> > >
> > > Benchmark 1: git-upload-pack (HEAD~)
> > > Time (mean ± σ): 7.113 s ± 0.028 s [User: 6.900 s, System: 0.662 s]
> > > Range (min … max): 7.072 s … 7.168 s 10 runs
> > >
> > > Benchmark 2: git-upload-pack (HEAD)
> > > Time (mean ± σ): 6.622 s ± 0.061 s [User: 6.452 s, System: 0.650 s]
> > > Range (min … max): 6.535 s … 6.727 s 10 runs
> > >
> > > Summary
> > > 'git-upload-pack (HEAD)' ran
> > > 1.07 ± 0.01 times faster than 'git-upload-pack (HEAD~)'
> >
> > Nice!
> >
> > > - o = parse_object(the_repository, &oid);
> > > + commit = lookup_commit_in_graph(the_repository, &oid);
> > > + if (commit)
> > > + o = &commit->object;
> > > + else
> > > + o = parse_object(the_repository, &oid);
> > > +
> >
> > This is a neat trick. I see that we've also done this trick in
> > revision.c:get_reference(). Perhaps it is worth creating a helper,
> > maybe named parse_probably_commit()?
>
> That might be a good idea, thanks. I'll have a look at what the end
> result would look like.
>
> Patrick
I had a look at existing callsites which use `lookup_commit_in_graph()`,
but I found that it wasn't easily possible to convert them all to use a
new helper like you propose. Most of them have some custom logic like
skipping `parse_object()` if it's part of a promisor pack, so I really
only found two locations where such a new helper could be used without
also adding and supporting flags. I don't really think that's worth it
for now.
Patrick
> > > if (!o) {
> > > packet_writer_error(writer,
> > > "upload-pack: not our ref %s",
> > > @@ -1434,7 +1440,7 @@ static int parse_want_ref(struct packet_writer *writer, const char *line,
> > > if (skip_prefix(line, "want-ref ", &refname_nons)) {
> > > struct object_id oid;
> > > struct string_list_item *item;
> > > - struct object *o;
> > > + struct object *o = NULL;
> > > struct strbuf refname = STRBUF_INIT;
> > >
> > > strbuf_addf(&refname, "%s%s", get_git_namespace(), refname_nons);
> > > @@ -1448,7 +1454,15 @@ static int parse_want_ref(struct packet_writer *writer, const char *line,
> > > item = string_list_append(wanted_refs, refname_nons);
> > > item->util = oiddup(&oid);
> > >
> > > - o = parse_object_or_die(&oid, refname_nons);
> > > + if (!starts_with(refname_nons, "refs/tags/")) {
> > > + struct commit *commit = lookup_commit_in_graph(the_repository, &oid);
> > > + if (commit)
> > > + o = &commit->object;
> > > + }
> > > +
> > > + if (!o)
> > > + o = parse_object_or_die(&oid, refname_nons);
> > > +
> >
> > Even here, we _could_ use a parse_probably_commit() helper
> > inside the if (!starts_with(...)) block, even though we would
> > still need the if (!o) check later.
> >
> > Thanks,
> > -Stolee
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