Re: [RFC] git-split: Split the history of a git repository by subdirectories and ranges

From: Linus Torvalds <torvalds@osdl.org>
Date: Oct 23, 2006, 21:06 UTC
Message-ID: <Pine.LNX.4.64.0610231402560.3962@g5.osdl.org>
In-Reply-To: <453D2B98.8010903@freedesktop.org>

On Mon, 23 Oct 2006, Josh Triplett wrote:

> 
> Or have I misunderstood the case you have concerns about?  Why would the
> "nice" format incur additional cost?

Try it. The default "extreme" simplification is a _hell_ of a lot faster than doing the full history.

	[torvalds@g5 linux]$ time git-rev-list --full-history --parents HEAD -- kernel/sched.c >/dev/null

	real    0m4.660s
	user    0m4.612s
	sys     0m0.044s

	[torvalds@g5 linux]$ time git-rev-list --parents HEAD -- kernel/sched.c >/dev/null
	
	real    0m1.684s
	user    0m1.680s
	sys     0m0.004s

and the "nice" thing will be much slower still: just trying to figure out whether a commit is a parent of another commit is expensive. Doing so for _each_ merge is more expensive still. I think it's O(n^3), but what do I know..

			Linus