Re: [PATCH 2/7] Simple Performance Counters: x86_64 support

[Andi Kleen]

On Wed, Aug 01, 2007 at 11:45:39AM -0700, Christoph Lameter wrote:
> On Wed, 1 Aug 2007, Andi Kleen wrote:
> 
> > > It is certainly interesting to compare alternative ways of handling the 
> > > instruction streams by various processors or models of processors.
> > 
> > Well you have to do a lot more work then to handle instable TSCs then.
> 
> I have been using this for 2 years. It works fine for my purposes.

That might be on your systems, but for a mainline submission the
standards are higher.

> 
> > In particular the frequencies can be different between CPUs, they 
> > change (which you can catch with cpufreq notifiers) and during the
> > cpufreq change period they're instable (as in you can't tell for
> > some time which frequency they're currently running at and they
> > might be running immediate frequencies) 
> 
> Well then simply make sure that they do not change while you measure.

That would be a merge blocker in my opinion. Suitable for local
hacks, but nothing we want in tree.

-Andi

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/