Re: [RFD/PATCH] Implement pack.compression and pack-objects --compression=N

["Dana How" <danahow@gmail.com>]

On 5/4/07, Nicolas Pitre <nico@cam.org> wrote:
> On Thu, 3 May 2007, Junio C Hamano wrote:
>
> > "Dana How" <danahow@gmail.com> writes:
> >
> > > So for a 25% increase in blob size I get 33% less elapsed time
> > > in git-add, all by changing core.compression from -1 to 1.
> > > I'll definitely take that improvement.  [For the compressible files
> > > we typically have, using 0 is a bad idea:  the CPU "advantage"
> > > is swamped out by the time to write a much larger file.]
> >
> > The above number is about loose objects, right?
> >
> > > Since I don't care [to the same degree] about the responsiveness of
> > > packing,  I'd rather pack with -1 or better to keep packs small.
> >
> > I see.  You are saying that the fact that core.compression is
> > used also for packing makes the variable less useful.
>
> I think that would make sense to have separate configs for pack and
> loose object compression.  When not specified they should simply default
> to core.compression if it exists.  Otherwise I'd suggest that pack
> compression default level be Z_DEFAULT_COMPRESSION and loose object
> compression default level be Z_BEST_SPEED.  This would make interactive
> operations like git-add and git-commit even faster by default.

I agree with your Z_BEST_SPEED idea.  I did not include it in
the patch b/c I didn't want to change any behavior in the absence
of new config settings.

Are you actually arguing for *3* different compression-related config
variables?  How about:
(a) core.compression controls loose objects. defaults to Z_BEST_SPEED.
(b) pack.compression controls packing. defaults to Z_DEFAULT_COMPRESSION
if neither variable exists. defaults to core.compression if only that exists

The last sentence mimics current behavior and to me seems least
surprising.  Or pack.compression could be simpler: default to
Z_DEFAULT_COMPRESSION if pack.compression doesn't exist
(no interaction with core.compression).

Thanks,
-- 
Dana L. How  danahow@gmail.com  +1 650 804 5991 cell