From: "Shawn O. Pearce" <spearce@spearce•org>
To: Steven Grimm <koreth@midwinter•com>
Cc: Nicolas Pitre <nico@cam•org>, Sam Vilain <sam@vilain•net>,
Junio C Hamano <junkio@cox•net>,
Daniel Barkalow <barkalow@iabervon•org>,
Theodore Ts'o <tytso@mit•edu>,
Git Mailing List <git@vger•kernel.org>
Subject: Re: [PATCH] Add --no-reuse-delta option to git-gc
Date: Mon, 11 Jun 2007 02:31:18 -0400 [thread overview]
Message-ID: <20070611063118.GF6073@spearce.org> (raw)
In-Reply-To: <466CE998.9000706@midwinter.com>
Steven Grimm <koreth@midwinter•com> wrote:
> Nicolas Pitre wrote:
> >
> >It won't happen for a simple reason: to be backward compatible with
> >older GIT clients. If you have your repo compressed with bzip2 and an
> >old client pulls it then the server would have to decompress and
> >recompress everything with gzip. If instead your repo remains with gzip
> >and a new client asks for bzip2 then you have to recompress as well
> >(slow). So in practice it is best to remain with a single compression
> >method.
> >
>
> Not that I really think this is all that important (my original question
> was more out of curiosity than anything) but I don't think those are
> really issues.
...
> And since the hypothetical new client would have support for both
> compression types, pulling from a gzip-based repo could be accomplished
> totally transparently; you could, one assumes, even pull from a gzip
> repo and pack locally using the other scheme if you felt like it.
Right, I agree with Steven here.
Pack v4 (which is rapidly becoming vaporware it seems) uses such
a radically different encoding for its commit and tree objects
that you cannot send them as-is to a client unless that client
also understands pack v4. Consequently you need to decompress and
recompress those objects when talking to an older peer; this isn't
very different from a switch to bzip2.
That said, I think switching to a different generic compressor isn't
that interesting. We can probably do a lot better by organizing
files into clusters, where those clusters have large number of
symbols in common, and then compress everything in the same cluster
with the same pack-wide dictionary.
Specifically I'm thinking that you may be able to cluster the *.h/*.c
into one cluster, and the Makefile into another, and the .gitignore
into a third cluster, and then leverage the large commonalities
between those blobs when building a dictionary and compressing them.
No, I haven't prototyped it out yet.
--
Shawn.
next prev parent reply other threads:[~2007-06-11 6:31 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-08 2:54 [PATCH] Add --no-reuse-delta, --window, and --depth options to git-gc Theodore Ts'o
2007-05-08 3:13 ` Nicolas Pitre
2007-05-08 3:21 ` Theodore Tso
2007-05-08 3:38 ` Dana How
2007-05-08 4:43 ` Junio C Hamano
2007-05-08 13:28 ` [PATCH] Add --no-reuse-delta, --window, and --depth options to Theodore Ts'o
2007-05-08 13:28 ` [PATCH] Add pack.depth option to git-pack-objects and change default depth to 50 Theodore Ts'o
2007-05-08 13:28 ` [PATCH] Add --no-reuse-delta option to git-gc Theodore Ts'o
2007-05-08 15:35 ` Nicolas Pitre
2007-05-09 5:05 ` Daniel Barkalow
2007-05-09 8:15 ` Junio C Hamano
2007-05-09 9:02 ` Steven Grimm
2007-05-09 11:35 ` Other compression?, was " Johannes Schindelin
2007-05-09 15:15 ` Junio C Hamano
2007-05-09 19:10 ` Shawn O. Pearce
2007-06-10 7:40 ` Sam Vilain
2007-06-11 1:51 ` Nicolas Pitre
2007-06-11 6:20 ` Steven Grimm
2007-06-11 6:31 ` Shawn O. Pearce [this message]
2007-06-11 10:20 ` Johannes Schindelin
2007-06-11 14:01 ` Nicolas Pitre
2007-06-11 21:40 ` Johannes Schindelin
2007-05-09 19:48 ` [PATCH] Add --aggressive option to 'git gc' Theodore Tso
2007-05-09 20:19 ` Junio C Hamano
2007-05-09 22:22 ` Theodore Tso
2007-05-10 7:38 ` Junio C Hamano
2007-05-08 15:38 ` [PATCH] Add pack.depth option to git-pack-objects and change default depth to 50 Nicolas Pitre
2007-05-08 16:30 ` Theodore Tso
2007-05-08 16:49 ` Johannes Schindelin
2007-05-08 18:09 ` Theodore Tso
2007-05-08 18:46 ` Nicolas Pitre
2007-05-09 13:49 ` Theodore Tso
2007-05-09 14:17 ` Johannes Schindelin
2007-05-08 17:07 ` Dana How
2007-05-08 17:35 ` Nicolas Pitre
2007-05-09 5:03 ` Junio C Hamano
2007-05-08 15:30 ` [PATCH] Add --no-reuse-delta, --window, and --depth options to Nicolas Pitre
2007-05-08 21:12 ` Junio C Hamano
2007-05-08 23:59 ` Nicolas Pitre
2007-05-08 13:46 ` [PATCH] Add --no-reuse-delta, --window, and --depth options to git-gc Nicolas Pitre
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