Re: [PATCH] fetch-pack: speed up loading of refs via commit graph

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Aug 5, 2021, 19:05 UTC
Message-ID: <87y29fzp5f.fsf@evledraar.gmail.com>
In-Reply-To: <YQr/vLNjZomIe1ME@coredump.intra.peff.net>

On Wed, Aug 04 2021, Jeff King wrote:

Show 9 quoted lines

> [...]
> If we don't go that route, there's another possible speedup: after
> parsing a tag, the type of tag->tagged (if it is not NULL) will be known
> from the tag's contents, and we can avoid the oid_object_info_extended()
> type lookup. It might need some extra surgery to convince the tag-parse
> not to fetch promisor objects, though.
>
> I'm not sure it would make that big a difference, though. If we save one
> type-lookup per parsed tag, then the tag parsing is likely to dwarf it.

Except that the tag type can be a lie, as our tests and some recent object/fsck serieses (not yet integrated) from me show. It can be relied upon for >99.99% of cases, but code like that needs to make sure it's not segfaulting or whatever if that relationship doesn't hold.