From: Josef Wolf <jw@raven.inka.de>
To: git@vger.kernel.org
Subject: Re: Re-Transmission of blobs?
Date: Thu, 12 Sep 2013 12:35:32 +0200 [thread overview]
Message-ID: <20130912103531.GD14259@raven.wolf.lan> (raw)
In-Reply-To: <20130912092339.GA30702@sigill.intra.peff.net>
On Do, Sep 12, 2013 at 05:23:40 -0400, Jeff King wrote:
> On Thu, Sep 12, 2013 at 09:42:41AM +0200, Josef Wolf wrote:
>
> I think Junio is referring to the reachability bitmap work. We may know
> that the other side has commit "E" (and therefore every object reachable
> from it), but we do not walk the graph to find the complete set of
> reachable objects. Doing so requires a lot of CPU and I/O, and in most
> cases does not help much.
I'm not sure I understand correctly. I see that bitmaps can be used to
implement set operations. But how comes that walking the graph requires a lot
of CPU? Isn't it O(n)?
> However, if we had an index of reachable objects (e.g., a bitmap) for
> each commit, then we could very cheaply compute the set difference
> between what the other side wants and what they have.
Those bitmaps would be stored in the git metadata? Is it worth it? Storing a
bitmap for every commit just to be used once-in-a-while seems to be a pretty
big overhead to me. Not to mention the interoperability problems you mentioned
below.
> JGit has support for pack bitmaps already. There was a patch series a
> few months ago to implement a similar functionality for C git, but the
> on-disk format was not compatible with JGit's. That series has been
> reworked off-list to be compatible with the JGit implementation.
>
> Those patches need a little cleanup before they are ready for the list,
> but hopefully that should happen soon-ish.
Sounds like you're already almost done and don't really need help
anymore. Just out of curiosity, I'd be interested in a pointer anyway ;-)
--
Josef Wolf
jw@raven.inka.de
next prev parent reply other threads:[~2013-09-12 10:40 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-10 13:08 Re-Transmission of blobs? Josef Wolf
2013-09-10 17:51 ` Junio C Hamano
2013-09-11 11:27 ` Josef Wolf
2013-09-11 17:14 ` Junio C Hamano
2013-09-12 7:42 ` Josef Wolf
2013-09-12 9:23 ` Jeff King
2013-09-12 10:35 ` Josef Wolf [this message]
2013-09-12 19:44 ` Jeff King
2013-09-13 10:09 ` Josef Wolf
2013-09-16 21:55 ` Jeff King
2013-09-20 9:27 ` Josef Wolf
2013-09-24 7:36 ` Jeff King
2013-09-24 20:36 ` Josef Wolf
2013-09-12 12:45 ` Pyeron, Jason J CTR (US)
2013-09-12 19:56 ` Jeff King
2013-09-12 20:06 ` Pyeron, Jason J CTR (US)
2013-09-13 10:23 ` Josef Wolf
2013-09-13 11:51 ` Jason Pyeron
2013-09-13 12:16 ` Duy Nguyen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130912103531.GD14259@raven.wolf.lan \
--to=jw@raven.inka.de \
--cc=git@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).