Re: Git packs friendly to block-level deduplication

From: Jeff King <peff@peff.net>
Date: Jan 25, 2018, 00:10 UTC
Message-ID: <20180125001015.GA17856@sigill.intra.peff.net>
In-Reply-To: <87607qyfci.fsf@evledraar.gmail.com>

On Thu, Jan 25, 2018 at 01:03:25AM +0100, Ævar Arnfjörð Bjarmason wrote:

Show 12 quoted lines

> > You may also want to use "--threads=1" to avoid non-determinism in the
> > generated packs. In theory, both repos would then produce identical base
> > packs, though it does not seem to do so in practice (I didn't dig in to
> > what the different may be).
> 
> ..and north of 20% with --threads=1.
>
> [...]
>
> Thanks. I'll look into that, although the above results (sans hacking on
> the core pack-objects logic) suggest that even once I create an island
> I'm getting at most 20%.

I think it may be worth figuring out where the two differ. With --no-reuse-object and --no-reuse-delta, I'd think that the pack generated for a particular apex commit would be totally deterministic, regardless of other objects available in the repo. But it's not for some reason.

-Peff