Re: [ANNOUNCE] Git v2.19.0-rc0

Jeff King wrote:

FWIW, it's not 10%. The best I measured was ~4% on a very
hashcmp-limited operation, and I suspect even that may be highly
dependent on the compiler. We might be able to improve more by
sprinkling more asserts around, but there are 75 mentions of
the_hash_algo->rawsz. I wouldn't want to an assert at each one.

I don't mind doing one or a handful of these asserts as part of v2.19 if
we want to try to reclaim those few percent. But I suspect the very
first commit in any further hash-transition work is just going to be to
rip them all out.

I was thinking just hashcmp and hashcpy.

Ideally such a change would come with a performance test to help the
person writing that very first commit.  Except we already have
performance tests that capture this. ;-)

For further hash-transition work, I agree someone may want to revert
this, and I don't mind such a revert appearing right away in "next".
And it's possible that we might have to do the equivalent of manual
template expansion to recover the performance in some
performance-sensitive areas.  Maybe we can get the compiler to
cooperate with us in that and maybe we can't.  That's okay with me.

Anyway, I'll resend your patch with a commit message added some time
this evening.

Thanks,
Jonathan