Re: Unresolved issues #2 (shallow clone again)

From: Theodore Tso <tytso@mit.edu>
Date: May 8, 2006, 00:33 UTC
Message-ID: <20060508003338.GB17138@thunk.org>
In-Reply-To: <20060507075631.GA24423@coredump.intra.peff.net>

On Sun, May 07, 2006 at 03:56:31AM -0400, Jeff King wrote:

Show 13 quoted lines

> On Sun, May 07, 2006 at 06:08:03PM +1200, Martin Langhoff wrote:
> 
> > >> And in any case commits and trees are lightweight and compress well...
> > >Commit maybe, but is this based on a hard fact?
> > No hard facts here :( but I think it's reasonable to assume that the
> > trees delta/compress reasonably well, as a given commit will change
> > just a few entries in each tree.
> 
> A few hard facts (using Linus' linux-2.6 tree):
>   - original packsize: 120996 kilobytes
>   - unpacked: 233338 objects, 1417476 kilobytes
>     This is an 11.7:1 compression ratio (of course, much of this is
>     wasted space from the 4k block size in the filesystem)

If there are 233338 objects, then the average wasted space due to internal fragmentation is 233338 * 2k, or 466676 kilobytes, or only 36% of the wasted space. Most of the savings is probably coming from the compression and delta packing.

						- Ted