Re: Summer of Code - Cached Packs/Object Lists

From: Nicolas Pitre <nico@cam.org>
Date: Mar 23, 2009, 14:41 UTC
Message-ID: <alpine.LFD.2.00.0903231037100.30483@xanadu.home>
In-Reply-To: <20090323025244.GO23521@spearce.org>

On Sun, 22 Mar 2009, Shawn O. Pearce wrote:

Show 16 quoted lines

> Thomas Coppi <thisnukes4u@gmail.com> wrote:
> > On Sun, Mar 22, 2009 at 7:59 PM, Shawn O. Pearce <spearce@spearce.org> wrote:
> >> You could do both. ??But I think most people on the list will argue
> >> that doing both is overkill and only one is necessary, and further,
> >> that only the one that offers the "biggest bank for the buck"
> >> should be implemented.
> >
> > Alright, that seems reasonable.  Given that I think I would lean
> > towards implementing an object list caching mechanism, since that seems
> > to be more generally applicable.  The logic for this would then need to
> > be in the rev-list code(as mentioned in the JGit discussion), correct?
> 
> Probably.  IIRC upload-pack forks a rev-list to produce the
> object list, and pipes that into the forked pack-objects' stdin.
> Thus rev-list is probably what would need to know how to include
> the cached list to its output.

Related to this, the first optimization is probably to avoid the fork altogether. The pack-objects code knows how to list objects by itself already, and that is used by git-repack. At the moment, packed tree objects during a fetch are probably accessed one extra time needlessly.

Nicolas