Re: git packs

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Nov 10, 2007, 06:53 UTC
Message-ID: <alpine.LFD.0.999.0711092244080.15101@woody.linux-foundation.org>
In-Reply-To: <alpine.LFD.0.999.0711092211250.15101@woody.linux-foundation.org>

On Fri, 9 Nov 2007, Linus Torvalds wrote:

Show 7 quoted lines

> 
> That said, I have worked with a 3GB pack-file (one of the KDE trial 
> repos). That worked fine. But git does tend to want a *lot* of memory for 
> really big repositories, so I suspect that if you actually work with 2GB+ 
> pack-files, you'll be wanting a 64-bit environment just because you'll be 
> wanting more than 2GB of physical RAM in order to be able to access it 
> efficiently.

Just double-checked. Yes, sirree. You definitely want 4GB+ if you are cloning a 3GB git pack-file. The "git-pack-objects" phase not only is going to walk all over the pack-file, it's going to add its own memory footprint on top of that just keeping track of all the objects.

So I doubt 2GB+ pack-files are all that practical on 32-bit hosts. At least not with the kind of performance behaviour *I* would accept.

(Of course, since git packs things pretty damn well, it would need to be a really really big project to be a 2GB+ pack-file, or just contain a lot of generally large non-deltable binary data file - one scenario where git definitely doesn't work wonderfully well, although I doubt many other SCM's do either..)

			Linus