From: Jeff King <peff@peff.net>
To: git@vger.kernel.org
Cc: Duy Nguyen <pclouds@gmail.com>, "Shawn O. Pearce" <spearce@spearce.org>
Subject: [PATCH/RFC 0/6] commit caching
Date: Tue, 29 Jan 2013 04:14:34 -0500 [thread overview]
Message-ID: <20130129091434.GA6975@sigill.intra.peff.net> (raw)
This is the cleaned-up version of the commit caching patches I mentioned
here:
http://article.gmane.org/gmane.comp.version-control.git/212329
The basic idea is to generate a cache file that sits alongside a
packfile and contains the timestamp, tree, and parents in a more compact
and easy-to-access format.
The timings from this one are roughly similar to what I posted earlier.
Unlike the earlier version, this one keeps the data for a single commit
together for better cache locality (though I don't think it made a big
difference in my tests, since my cold-cache timing test ends up touching
every commit anyway). The short of it is that for an extra 31M of disk
space (~4%), I get a warm-cache speedup for "git rev-list --all" of
~4.2s to ~0.66s.
The big thing it does not (yet) do is use offsets to reference sha1s, as
Shawn suggested. This would potentially drop the on-disk size from 84
bytes to 16 bytes per commit (or about 6M total for linux.git).
Coupled with using compression level 0 for trees (which do not compress
well at all, and yield only a 2% increase in size when left
uncompressed), my "git rev-list --objects --all" time drops from ~40s to
~25s. Perf reveals that we're spending most of the remaining time in
lookup_object. I've spent a fair bit of time trying to optimize that,
but with no luck; I think it's fairly close to optimal. The problem is
just that we call it a very large number of times, since it is the
mechanism by which we recognize that we have already processed each
sha1.
[1/6]: csum-file: make sha1write const-correct
[2/6]: strbuf: add string-chomping functions
[3/6]: introduce pack metadata cache files
[4/6]: introduce a commit metapack
[5/6]: add git-metapack command
[6/6]: commit: look up commit info in metapack
-Peff
next reply other threads:[~2013-01-29 9:15 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-29 9:14 Jeff King [this message]
2013-01-29 9:15 ` [PATCH 1/6] csum-file: make sha1write const-correct Jeff King
2013-01-29 9:15 ` [PATCH 2/6] strbuf: add string-chomping functions Jeff King
2013-01-29 10:15 ` Michael Haggerty
2013-01-29 11:10 ` Jeff King
2013-01-30 5:00 ` Michael Haggerty
2013-01-29 9:15 ` [PATCH 3/6] introduce pack metadata cache files Jeff King
2013-01-29 17:35 ` Junio C Hamano
2013-01-30 6:47 ` Jeff King
2013-01-30 1:30 ` Duy Nguyen
2013-01-30 6:50 ` Jeff King
2013-01-29 9:16 ` [PATCH 4/6] introduce a commit metapack Jeff King
2013-01-29 10:24 ` Michael Haggerty
2013-01-29 11:13 ` Jeff King
2013-01-29 17:38 ` Junio C Hamano
2013-01-29 18:08 ` Junio C Hamano
2013-01-30 7:12 ` Jeff King
2013-01-30 7:17 ` Junio C Hamano
2013-02-01 9:21 ` Jeff King
2013-01-30 15:56 ` Junio C Hamano
2013-01-31 17:03 ` Shawn Pearce
2013-02-01 9:42 ` Jeff King
2013-02-02 17:49 ` Junio C Hamano
2013-01-30 7:07 ` Jeff King
2013-01-30 3:36 ` Duy Nguyen
2013-01-30 7:12 ` Jeff King
2013-01-30 13:56 ` Duy Nguyen
2013-01-30 14:16 ` Duy Nguyen
2013-01-31 11:06 ` Duy Nguyen
2013-02-01 10:15 ` Jeff King
2013-02-02 9:49 ` Duy Nguyen
2013-02-01 10:40 ` Jeff King
2013-03-17 13:21 ` Duy Nguyen
2013-03-18 12:20 ` Jeff King
2013-02-01 10:00 ` Jeff King
2013-01-29 9:16 ` [PATCH 5/6] add git-metapack command Jeff King
2013-01-29 9:16 ` [PATCH 6/6] commit: look up commit info in metapack Jeff King
2013-01-30 3:31 ` [PATCH/RFC 0/6] commit caching Duy Nguyen
2013-01-30 7:18 ` Jeff King
2013-01-30 8:32 ` Duy Nguyen
2013-01-31 17:14 ` Shawn Pearce
2013-02-01 9:11 ` Jeff King
2013-02-02 10:04 ` Shawn Pearce
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