Re: [PATCH 14/19] [GSOC] cat-file: reuse ref-filter logic

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 12, 2021, 20:38 UTC
Message-ID: <xmqqtukz2rp4.fsf@gitster.g>
In-Reply-To: <CAP8UFD0vHw8cK90RbOUcrAcxNKiHVTMX0VEiK8+MNyHH0CNm4A@mail.gmail.com>

Christian Couder <christian.couder@gmail.com> writes:

Show 8 quoted lines

>> The performance for `git cat-file --batch-all-objects --batch
>> >/dev/null` on the Git repository itself with performance testing
>> tool `time` change from "27.37s user 0.29s system 98% cpu 28.089
>> total" to "33.69s user 1.54s system 87% cpu 40.258 total".
>
> Saying that a later patch will add a fast path which will mitigate the
> performance regression introduced by this patch might help reassure
> reviewers.

More importantly, why is such a fast-path even needed? Isn't it a sign that the ref-filter implementation is eating more cycles than it should for given set of placeholders? Do we know where the extra cycles goes?

I find it somewhat alarming if we are talking about "fast-path" workaround before understanding why we are seeing slowdown in the first place.