Re: [patch] perf_counter: Add p6 PMU

[Peter Zijlstra <peterz@infradead.org>]

On Wed, 2009-07-08 at 23:45 +0200, Peter Zijlstra wrote:
> On Wed, 2009-07-08 at 17:46 -0400, Vince Weaver wrote:
> > On Wed, 8 Jul 2009, Peter Zijlstra wrote:
> > 
> > >   doesn't sound like the right kind of event.. but then, it doesn't
> > >   have anything better either.
> > 
> > Is there a way to specify "invalid event"?  Just setting it to 0 doesn't 
> > work, on the Pentium Pro event 0 returns what looks like essentially
> > random numbers.
> 
> Hmm, bugger. I was assuming writing 0 to the evensel would disable the
> counter. Apparently that only works for eventsel1, which would mean we
> cannot run counter1 without counter0. That means we'd need to do a
> counter swap at times... :/

Ooh, we can instead use a counter that's specified to not count anything
for 'disabling' the counter, like event 0x2E with unit mask 0.