Re: [PATCH v3 0/5] Avoid spawning gzip in git archive

[Jeff King <peff@peff.net>]

On Fri, Jul 01, 2022 at 06:05:59PM +0200, Johannes Schindelin wrote:

> Stolee pointed out to me that objects inside pack files are also
> zlib-compressed, and that measuring the speed of `git rev-list --objects
> --all --count` might therefore be a better test.

That will spend quite a lot of time doing hash-lookups for each tree
entry. A better raw zlib test might be:

  git cat-file --batch --batch-all-objects --unordered >/dev/null

which will just dump each object, and should mostly be zlib and delta
reconstruction (the --unordered is important to hit the deltas in the
right order).

> And this is where things get a little messy: in the context of Git for
> Windows, my local measurements indicate that zlib is better, with ~41
> seconds using zlib vs ~52 seconds using zlib-ng (but the latter has a
> rather large variance).

That is a surprising slow-down between the two. I'd expect the command
above to show even more pronounced results, though, as it's spending
less time doing non-zlib things. But it's still just inflating (as
opposed to git-archive, which is both inflating and deflating).

-Peff