From: "René Scharfe" <l.s.r@web.de>
To: Jeff King <peff@peff.net>
Cc: Keegan Carruthers-Smith <keegan.csmith@gmail.com>, git@vger.kernel.org
Subject: Re: git archive generates tar with malformed pax extended attribute
Date: Sun, 2 Jun 2019 18:58:48 +0200 [thread overview]
Message-ID: <c961d89d-db0b-597f-c183-81aa791c0987@web.de> (raw)
In-Reply-To: <20190530115554.GB31607@sigill.intra.peff.net>
Am 30.05.19 um 13:55 schrieb Jeff King:
> On Wed, May 29, 2019 at 07:54:44PM +0200, René Scharfe wrote:
>
>> Am 29.05.19 um 03:17 schrieb Jeff King:
>>> But here the problem is in the tree, not the blob. So we're not finding
>>> suspect blobs, but rather re-checking each tree. And no matter what we
>>> do (whether it's visiting the object again, or creating a set or mapping
>>> with the object names) is going to be linear there. And a repository
>>> with a symlink in the root tree is going to revisit or put in our
>>> mapping every single root tree.
>>
>> That's true, potentially it needs remember and/or reprocess all trees,
>> meaning this check may double the run time of fsck in the worst case.
>> Example from the wild: The kernel repo currently has 36 symlinks and
>> 6+ million objects are checked in total, and the symlink check processes
>> 18943 trees_with_symlinks entries there.
>
> That sounds about right. It's basically every version of every tree that
> has a symlink. Did it make a noticeable difference in timing? Indexing
> the whole kernel history is already a horribly slow process. :)
Right, I didn't notice a difference -- no patience for watching that
thing to the end. But here are some numbers for v2.21.0 vs. master with
the patch:
Benchmark #1: git fsck
Time (mean ± σ): 307.775 s ± 9.054 s [User: 307.173 s, System: 0.448 s]
Range (min … max): 294.052 s … 322.931 s 10 runs
Benchmark #2: ~/src/git/git fsck
Time (mean ± σ): 319.754 s ± 2.255 s [User: 318.927 s, System: 0.671 s]
Range (min … max): 316.376 s … 323.747 s 10 runs
Summary
'git fsck' ran
1.04 ± 0.03 times faster than '~/src/git/git fsck'
Seeing only a single CPU core being stressed for that long is a bit sad
to see. Checking individual objects should be relatively easy to
parallelize, shouldn't it?
René
next prev parent reply other threads:[~2019-06-02 16:59 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-24 6:45 git archive generates tar with malformed pax extended attribute Keegan Carruthers-Smith
2019-05-24 7:06 ` Jeff King
2019-05-24 7:35 ` Keegan Carruthers-Smith
2019-05-24 8:13 ` Jeff King
2019-05-25 13:26 ` René Scharfe
2019-05-25 13:46 ` Andreas Schwab
2019-05-25 21:07 ` Ævar Arnfjörð Bjarmason
2019-05-26 21:33 ` René Scharfe
2019-05-28 5:44 ` Jeff King
2019-05-28 5:58 ` Jeff King
2019-05-28 18:01 ` René Scharfe
2019-05-28 19:08 ` Jeff King
2019-05-28 23:34 ` René Scharfe
2019-05-29 1:17 ` Jeff King
2019-05-29 17:54 ` René Scharfe
2019-05-30 11:55 ` Jeff King
2019-06-02 16:58 ` René Scharfe [this message]
2019-06-04 20:53 ` Jeff King
2019-05-27 5:11 ` Keegan Carruthers-Smith
2019-05-25 20:46 ` Ævar Arnfjörð Bjarmason
2019-05-25 21:19 ` brian m. carlson
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