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From: Jeff King <peff@peff.net>
To: Patrick Steinhardt <ps@pks.im>
Cc: Derrick Stolee <stolee@gmail.com>, git@vger.kernel.org
Subject: Re: [PATCH] bitmaps: don't recurse into trees already in the bitmap
Date: Tue, 22 Jun 2021 15:39:55 -0400	[thread overview]
Message-ID: <YNI8iyzObjxH0/ED@coredump.intra.peff.net> (raw)
In-Reply-To: <YNG/05+fmA0YPKj7@ncase>

On Tue, Jun 22, 2021 at 12:47:57PM +0200, Patrick Steinhardt wrote:

> Today I've been experimenting with the connectivity check of
> git-receive-pack(1) once again to see whether I'm able to get a
> performance improvement if the git-rev-list(1) command spawned as part
> of the connectivity check uses `--use-bitmap-index`.
> 
> Turns out the answer is "no": it has exactly the same performance
> characteristics when pushing into a bitmapped repository (linux.git)
> compared to the version not using a bitmap index, except for once case
> where it performs 70x worse: force-pushing "master~10:master" into a
> bitmapped repo takes 11s instead of 0.15s with bitmaps enabled.
> 
> Just leaving this here as a note for anybody (or myself) to pick up at a
> later point.

Thanks. I'd wager that's probably the "we find the exact bitmap for the
'haves'" problem. There are probably a lot of old refs with so-so bitmap
coverage, and we traverse all of them down to the nearest bitmap. If we
filled in the bitmap by traversing commits in timestamp or generation
order and ending at the merge-base, we could probably avoid looking at
them at all.

-Peff

      reply	other threads:[~2021-06-22 19:42 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-14  7:27 [PATCH] bitmaps: don't recurse into trees already in the bitmap Jeff King
2021-06-14 12:05 ` Jeff King
2021-06-15 14:17   ` Derrick Stolee
2021-06-16 12:31     ` Patrick Steinhardt
2021-06-18 12:59       ` Jeff King
2021-06-18 13:35         ` Patrick Steinhardt
2021-06-18 14:10           ` Jeff King
2021-06-22 10:47           ` Patrick Steinhardt
2021-06-22 19:39             ` Jeff King [this message]

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