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

On Thu, Aug 05, 2021 at 09:05:59PM +0200, Ævar Arnfjörð Bjarmason wrote:

On Wed, Aug 04 2021, Jeff King wrote:

quoted

[...]
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.

Yes, but we'd discover that when we called repo_parse_commit(), and
Patrick's patch already handles failure there.

-Peff