Re: cloning the kernel - why long time in "Resolving 313037 deltas"

From: Linus Torvalds <torvalds@osdl.org>
Date: Dec 19, 2006, 16:57 UTC
Message-ID: <Pine.LNX.4.64.0612190855300.3479@woody.osdl.org>
In-Reply-To: <20061219161919.GA16980@thunk.org>

On Tue, 19 Dec 2006, Theodore Tso wrote:

> 
> So the main reason to use mamp, as Linus puts it, is if the management
> overhead of needing to read lots of small bits of the file makes the
> use of malloc/read to be a pain in the *ss, then go for it.

An example of this in git is the regular pack-file accesses. We're MUCH better off just mmap'ing the whole pack-file (or at least big chunks of it) and not having to maintain difficult structures of "this is where I read that part of the file into memory", or read _big_ chunks when quite often we just use a few kB of it.

So mmap for pack-files does make sense, but probably only when you can mmap big chunks, and are going to access much smaller (random) parts of it.