Re: Rd: [RFC] dl-procinfo and HWCAP_IMPORTANT support for powerpc

[Benjamin Herrenschmidt <benh at kernel dot crashing dot org>]

On Thu, 2005-12-22 at 20:13 -0600, Tom Gall wrote:
> Food for thought .. but if there are good reasons for having perfect 
> detail as to the processor one is on, why not just send on the PVR and be done 
> with it.

Because you may not need the actual revision :) Anyway, the idea of
using a doublet is just something that came to mind while I was typing,
not a properly thought out thing. I still think the micro architecture
should be out of the HWCAP or we'll just overflow the field.

> > I think it was a mistake to add the microarch like POWER4 in there. It
> > should have been a separate entity, possibly the ELF_PLATFORM string.
> > The change was done in a rush but not properly thought out (and that's
> > partially my fault too).
> > 
> 
> Perhaps we ought to compile the performance impacts one might want to 
> consider so we can continue discussions on what all might (and might not) 
> be reason to make sure that whatever design we end up with is going to 
> fit. 

Yes, well, my main worry is running out of HWCAP bits very soon if we
add microarchitectures there. Especially if we start having the embedded
stuff in.

> > In addition, it might be worth using the vdso for some very processor
> > specific things, thus getting the benefit automatically without
> > requiring a different libc. I've been pondering putting implementations
> > of memcpy and spinlocks in there... food for thoughts at this point
> > though.
> 
> Personally I think this is good food for thought....  sorta dark chocolate 
> in the cubboard ... yearning to be eaten ... :-)

Yah, good idea :)

Ben.