On Tue, 10 Jun 2008 09:56:18 -0400
Richard Freeman <rich0@g.o> wrote:
> Joe Peterson wrote:
> > No, I have not profiled PMs to try this, but you are saying that
> > reading the first few lines of a file is not faster than sourcing
> > the whole thing with bash?  Remember that it could abort the minute
> > it sees a non '#' or blank line, which would be after the first few.
> > 
> 
> Actually, if you specified that the EAPI goes on the first line, then 
> you'd only need to read the first line.
> 
> And to the extent that the rest got read into memory anyway by the 
> kernel, well then it is already in the cache when whatever mechanism
> is invoked to parse the rest of the file.

Except that currently, the ebuild file isn't opened for read. So it's
not in memory at all.

> I don't think that filename-vs-first-line is going to make a big 
> difference in practical performance.

It's about a factor of five difference in cold-cache resolution
performance for Paludis.

-- 
Ciaran McCreesh