Re: [Gnu-arch-users] Re: Re: [arch-users] advanced usage advice: the prism technique (fwd)

[Andrea Arcangeli]

On Sat, Sep 27, 2003 at 12:30:34PM +0100, Stig Brautaset wrote:
> On Sep 27 2003, Andrea wrote:
> > > On the other hand, if you want to share project trees, which are
> > > essentially unrelated in terms of arch, it's probably better to use an
> > > external tool to hard-link files with identical content.  I have some
> > 
> > this tool already exists and it's attached (it was in a very very old
> > package called perforate that I still use sometime in source form)
> > careful, it destroys all the permissions so don't run it on /dev ;)
> > 
> >     finddup | nodup
> > 
> > they're small enough that I attached it.
> > 
> > Yes, that would save the duplication of space, but it would be slow (it
> > sure can be improved in performance though) and it would still not
> > address the speed of a 'get' of a pure tree.
> > 
> > Besides the space argument, one of the main properties of cp -la is that
> > it takes nothing, unlike a cp -a or a tar xzf of a 500m payload similar
> > to the 2.6 kernel.
> > 
> > > ideas for speeding up such a tool by caching (in fact I've recently
> > > written something quite similar for my maildir folders).  This would
> > > still result in full-tree copies if you use certain merging methods
> > > (probably just "update"), but otherwise, it should come pretty close to
> > > what you want.
> > > 
> > > Or am I missing something?
> > 
> > I don't think you're missing anything.
> 
> Revision libraries already consist of hardcoded files to save space. How

yes.

> about adding an argument to `tla get' so that it would hardlink instead
> of copying files from the revision library (if possible)? It escapes my

that would make it. Of course I'm playing risky, but I'm fine to deal
with that risk, the payoff makes it worthwhile, it's simply up to me
(not to the kernel since the kernel can't do that) to always do
copy-on-write on all the checked out trees.

Andrea - If you prefer relying on open source software, check these links:
            rsync.kernel.org::pub/scm/linux/kernel/bkcvs/linux-2.[45]/
            http://www.cobite.com/cvsps/
            svn://svn.kernel.org/linux-2.[46]/trunk