Re: [RFC] Cache negative delta pairs

From: Nicolas Pitre <nico@cam.org>
Date: Jun 29, 2006, 21:47 UTC
Message-ID: <Pine.LNX.4.64.0606291743010.1213@localhost.localdomain>
In-Reply-To: <Pine.LNX.4.64.0606291428150.12404@g5.osdl.org>

On Thu, 29 Jun 2006, Linus Torvalds wrote:

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> 
> 
> On Thu, 29 Jun 2006, Nicolas Pitre wrote:
> >
> > On Thu, 29 Jun 2006, Linus Torvalds wrote:
> > 
> > > Instead of having a separate cache, wouldn't it be much better to just 
> > > take the hint from the previous pack-file?
> > 
> > DOH!  ;-)
> 
> Btw, I think this could do with a flag to turn it on/off (but probably 
> default to on).

I think it should simply be coupled with the --no-reuse-delta flag.

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> The advantage of this patch is that it should guarantee that if everything 
> is already packed, a repack will basically keep the pack identical. 
> 
> However, that is obviously also the dis-advantage, since it means that 
> repacking cannot improve packing. So adding a flag to say "please try to 
> incrementally improve the pack" might well be worth it, even if this new 
> behaviour would be the _default_.

Actually, the delta reusing already prevents those deltas from being improved. So your patch only extend this notion to the non-deltified objects as well. And the way out is to provide the --no-reuse-delta flag.

Nicolas