Re: We should add a "git gc --auto" after "git clone" due to commit graph

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 8, 2018, 23:02 UTC
Message-ID: <xmqqd0skt53o.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20181008164141.GZ23446@szeder.dev>

SZEDER Gábor <szeder.dev@gmail.com> writes:

Show 17 quoted lines

> There is certainly potential there.  With a (very) rough PoC
> experiment, a 8MB bloom filter, and a carefully choosen path I can
> achieve a nice, almost 25x speedup:
>
>   $ time git rev-list --count HEAD -- t/valgrind/valgrind.sh
>   6
>
>   real    0m1.563s
>   user    0m1.519s
>   sys     0m0.045s
>
>   $ time GIT_USE_POC_BLOOM_FILTER=y ~/src/git/git rev-list --count HEAD -- t/valgrind/valgrind.sh
>   6
>
>   real    0m0.063s
>   user    0m0.043s
>   sys     0m0.020s

Even though I somehow sense a sign of exaggeration in [v] in the pathname, it still is quite respectable.

>   bloom filter total queries: 16269 definitely not: 16195 maybe: 74 false positives: 64 fp ratio: 0.003934
>
> But I'm afraid it will take a while until I get around to turn it into
> something presentable...

That's OK.  This is an encouraging result.

Just from curiousity, how are you keying the filter? tree object name of the top-level and full path concatenated or something like that?