Re: [RFC] Cache negative delta pairs

From: Jeff King <peff@peff.net>
Date: Jun 29, 2006, 21:37 UTC
Message-ID: <20060629213728.GB15604@coredump.intra.peff.net>
In-Reply-To: <Pine.LNX.4.64.0606291616480.1213@localhost.localdomain>

On Thu, Jun 29, 2006 at 04:24:01PM -0400, Nicolas Pitre wrote:

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> > Obviously the kernel repo is doing better, but x=500 is only 4 days ago.
> > Trying with --before=2.weeks.ago yields only 31505 matches.
> 
> What does this prove?  I fail to see the relation between those results 
> and a possible git-pack-objects improvement.

My point is that the window cache gets invalidated over time, whereas a sha1 by sha1 cache doesn't. However, the point is moot, as I think Linus has come up with a much better solution.

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> The negative delta cache concept is certainly attractive even for normal 
> repositories, especially for public servers, since when used in 
> conjonction with delta reuse it makes the creation of a pack basically 
> free.  So I think this idea really has merits, as long as the cache 
> remains small.

Yes, if you're talking about a situation in which you make many packs for a given set of commits, then it does make more sense (what I was really trying to eliminate was a 10 minute repack followed by another 10 minute repack to push to the server).

-Peff