On Mon, Mar 20, 2017 at 07:24:12PM +0100, Ævar Arnfjörð Bjarmason wrote:
> On Mon, Mar 20, 2017 at 5:33 PM, Michael Haggerty <mhag...@alum.mit.edu> > wrote: > > > I've completed a draft of an epic 48-patch series implementing all of > > the above points on my GitHub fork [1] as branch > > `wip/mmap-packed-refs`. It dramatically speeds up performance and > > reduces memory usage for some tasks in repositories with very many > > packed references. > > Just curious, what sort of performance numbers on mainly what sort of > operations? I'd expect the fixed cost of e.g. `git log -1 >/dev/null` > to go down, which can take as long as a second on some repos with a > huge amount of refs, but anything else? Anything that reads refs (and that includes anything that touches an object, because it looks at refs/replace) loads the entire packed-refs file into memory. So I'd expect you're paying that "1 second" cost on a lot of commands. Even commands that traverse the entire ref namespace should improve, as we'd spend a lot less time allocating and copying data into the in-memory refs cache. Not to mention that the memory usage is reduced, though that probably only really matters for pathological cases. -Peff
