Messages in this thread | | | Date | Mon, 13 Oct 2008 20:22:22 +0100 | Subject | Re: [PATCH] Mention Intel Atom in Kconfig.cpu | From | "Phil Endecott" <> |
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Arjan van de Ven wrotes: > On Mon, 13 Oct 2008 17:02:30 +0300 > Adrian Bunk <bunk <at> kernel.org> wrote: > > > On Mon, Oct 13, 2008 at 09:30:14AM -0400, Arjan van de Ven wrote: > > > On Mon, 13 Oct 2008 15:30:51 +0200 > > > Andi Kleen <andi <at> firstfloor.org> wrote: > > > > > > > > > Core2 instruction set with tune=generic is still the best to > > > > > set. > > > > > > > > Not sure that is true. These option are mostly for the compiler. > > > > > > exactly, and our benchmarks show that tune=generic is best right now > > > for Atom. > > > (586 scheduling sounds nice, but the pipelines are rather different. > > > And the benchmarks don't lie.. > > > > That sounds a bit dangerous since tune=generic is documented to > > change the semantics between gcc versions to better fit more recent > > CPUs (there's even a small difference between gcc 4.2 and gcc 4.3): > > > > reality is that tune=generic avoids the things that are "really bad" > for a wide generation of cpus; the world of x86 is such that there > really are many common things that are good for the vast majority of > the cpus out there (or at least neutral). > > Future versions of GCC might have a specific ATOM model. Until they do, > tune=generic is the right thing based on tests over a few gcc versions. > Yes it's a bit fluid, but no gcc isn't going to suddenly go do stupid > things for currently mass-sold cpus.
Well, if the Intel experts can't even agree, what hope do I have of getting it right :-( I chose Core2 because I read somewhere that Atom was "feature compatible" with it, but of course that doesn't say anything about the optimal optimisations. I trust that someone will update Kconfig.cpu with their idea of the right choice for Atom eventually.
(Maybe there should be a way to auto-suggest the right setting for a native build based on /proc/cpuinfo? I think the gcc build process can do something like that.)
Cheers, Phil.
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