Re: optimized script [Was: ARM defconfig files]

[Nicolas Pitre]

On Tue, 13 Jul 2010, Olof Johansson wrote:

> On Tue, Jul 13, 2010 at 10:07:05AM +0200, Uwe Kleine-König wrote:
> > Hello,
> > 
> > On Tue, Jul 13, 2010 at 09:07:41AM +0200, Uwe Kleine-König wrote:
> > > Hi
> > > 
> > > On Mon, Jul 12, 2010 at 01:50:47PM -0600, Grant Likely wrote:
> > > > On Mon, Jul 12, 2010 at 1:34 PM, Linus Torvalds
> > > > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> > > > > On Mon, Jul 12, 2010 at 12:17 PM, Nicolas Pitre <nico@xxxxxxxxxxx> wrote:
> > > > >> I think Uwe could provide his script and add it to the kernel tree.
> > > > >> Then all architectures could benefit from it.  Having the defconfig
> > > > >> files contain only those options which are different from the defaults
> > > > >> is certainly more readable, even on x86.
> > > > >
> > > > > Quite possible. But maintainers would need to be on the lookout of
> > > > > people actually using the script, and refusing to apply patches that
> > > > > re-introduce the whole big thing.
> > > > 
> > > > I can (partially) speak for powerpc.  If ARM uses this approach, then
> > > > I think we can do the same.  After the defconfigs are trimmed, I
> > > > certainly won't pick up any more full defconfigs.
> > > I just restarted my script on the powerpc defconfigs basing on rc5, I
> > > assume they complete in a few days time.
> > So Stephen was faster than me.  I don't know yet how he optimised my
> > script, meanwhile I put some efforts into it, too by just checking lines
> > that match "^(# )?CONFIG_".
> > 
> > Find it attached.
> > 
> > I will start to reduce the remaining configs (i.e. all but arm and
> > powerpc).
> 
> I added just a simple heuristic: If I could remove a line, I attempted
> to remove twice the amount next time around (and fall back to 1 if it failed).
> 
[...]
> 
> While this script is great, it is somewhat painful to run given that it
> attempts one config per line. Even on a fast machine that tends to take
> a while.

The optimal solution is to add that .config reduction ability straight 
into the Kconfig parser (scripts/kconfig/*).  There you can find out 
right away what are the non default state for each config option without 
actually trying them out one by one.


Nicolas