From: "Alex Bennée" <kernel-hacker@bennee.com>
To: Thomas Rast <trast@inf.ethz.ch>
Cc: Ramkumar Ramachandra <artagnon@gmail.com>,
Git Mailing List <git@vger.kernel.org>
Subject: Re: Poor performance of git describe in big repos
Date: Thu, 30 May 2013 17:01:58 +0100 [thread overview]
Message-ID: <CAJ-05NOjVhb+3Cab7uQE8K3VE0Q2GhqR3FE=WzJZvSn8Djt6tw@mail.gmail.com> (raw)
In-Reply-To: <87ehcoeb3t.fsf@linux-k42r.v.cablecom.net>
On 30 May 2013 16:33, Thomas Rast <trast@inf.ethz.ch> wrote:
> Alex Bennée <kernel-hacker@bennee.com> writes:
>
>> 41.58% git libcrypto.so.1.0.0 [.] sha1_block_data_order_ssse3
>> 33.62% git libz.so.1.2.3.4 [.] inflate_fast
>> 10.39% git libz.so.1.2.3.4 [.] adler32
>> 2.03% git [kernel.kallsyms] [k] clear_page_c
>
> Do you have any large blobs in the repo that are referenced directly by
> a tag?
Most probably. I've certainly done a bunch of releases (which are tagged) were
the last thing that was updated was an FPGA image.
> Because this just so happens to exactly reproduce your symptoms:
>
> # in a random git.git
> $ time git describe --debug
> [...]
> real 0m0.390s
> user 0m0.037s
> sys 0m0.011s
> $ git tag big1 $(dd if=/dev/urandom bs=1M count=512 | git hash-object -w --stdin)
> 512+0 records in
> 512+0 records out
> 536870912 bytes (537 MB) copied, 45.5088 s, 11.8 MB/s
> $ time git describe --debug
> [...]
> real 0m1.875s
> user 0m1.738s
> sys 0m0.129s
> $ git tag big2 $(dd if=/dev/urandom bs=1M count=512 | git hash-object -w --stdin)
> 512+0 records in
> 512+0 records out
> 536870912 bytes (537 MB) copied, 44.972 s, 11.9 MB/s
> $ time git describe --debugsuche zur Beschreibung von HEAD
> [...]
> real 0m3.620s
> user 0m3.357s
> sys 0m0.248s
>
> (I actually ran the git-describe invocations more than once to ensure
> that they are again cache-hot.)
That looks pretty promising as a replication.
> git-describe should probably be fixed to avoid loading blobs, though I'm
> not sure off hand if we have any infrastructure to infer the type of a
> loose object without inflating it. (This could probably be added by
> inflating only the first block.) We do have this for packed objects, so
> at least for packed repos there's a speedup to be had.
Will it be loading the blob for every commit it traverses or just ones that hit
a tag? Why does it need to load the blob at all? Surely the commit
tree state doesn't
need to be walked down?
>
> --
> Thomas Rast
> trast@{inf,student}.ethz.ch
--
Alex, homepage: http://www.bennee.com/~alex/
next prev parent reply other threads:[~2013-05-30 16:02 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-30 10:38 Poor performance of git describe in big repos Alex Bennée
2013-05-30 11:33 ` Ramkumar Ramachandra
2013-05-30 13:09 ` Alex Bennée
2013-05-30 14:32 ` Ramkumar Ramachandra
2013-05-30 15:01 ` Alex Bennée
2013-05-30 15:17 ` Ramkumar Ramachandra
2013-05-30 15:33 ` Thomas Rast
2013-05-30 16:01 ` Alex Bennée [this message]
2013-05-30 16:21 ` Thomas Rast
2013-05-30 16:44 ` Thomas Rast
2013-05-30 19:01 ` Antoine Pelisse
2013-05-30 20:00 ` [PATCH 1/2] sha1_file: silence sha1_loose_object_info Thomas Rast
2013-05-30 20:00 ` [PATCH 2/2] lookup_commit_reference_gently: do not read non-{tag,commit} Thomas Rast
2013-05-30 21:22 ` Jeff King
2013-05-31 0:52 ` Duy Nguyen
2013-05-31 8:08 ` Thomas Rast
2013-05-31 16:00 ` Jeff King
2013-05-31 6:43 ` Ramkumar Ramachandra
2013-05-31 8:16 ` Thomas Rast
2013-05-30 19:30 ` Poor performance of git describe in big repos John Keeping
2013-05-31 8:14 ` Alex Bennée
2013-05-31 8:24 ` Thomas Rast
2013-05-31 8:40 ` Alex Bennée
2013-05-31 8:46 ` Thomas Rast
2013-05-31 9:57 ` Alex Bennée
2013-06-03 8:02 ` Alex Bennée
2013-06-03 16:32 ` Junio C Hamano
2013-06-03 17:48 ` Junio C Hamano
2013-05-31 10:27 ` Thomas Rast
2013-05-31 16:17 ` Jeff King
2013-06-03 8:39 ` Alex Bennée
2013-06-03 14:49 ` Jeff King
2013-05-31 8:32 ` John Keeping
2013-05-31 8:49 ` Alex Bennée
2013-05-31 8:59 ` John Keeping
2013-05-30 11:48 ` John Keeping
2013-05-30 12:29 ` Alex Bennée
2013-05-30 13:20 ` Duy Nguyen
[not found] ` <CAJ-05NPacjAEC99Ntd9eMnTD9_PMMYFob-_tAx5CeSB79TkRSg@mail.gmail.com>
2013-05-30 13:45 ` Duy Nguyen
2013-05-30 14:02 ` Alex Bennée
2013-05-30 13:16 ` Alex Bennée
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