Re: [PATCH 1/5] perf: Provide a proper stop action for softwareevents

From: Peter Zijlstra
Date: Thu Jun 10 2010 - 12:16:40 EST

On Thu, 2010-06-10 at 18:12 +0200, Frederic Weisbecker wrote:
> On Thu, Jun 10, 2010 at 01:10:42PM +0200, Peter Zijlstra wrote:
> > On Thu, 2010-06-10 at 12:46 +0200, Peter Zijlstra wrote:
> > >
> > > Something like the below would work, the only 'problem' is that it grows
> > > hw_perf_event.
> >
> > If we do the whole PAUSEd thing right, we'd not need this I think.
> It's not needed, and moreover software_pmu:stop/start() can be the same
> than software:pmu:disable/enable() without the need to add another check
> in the fast path.
> But we need perf_event_stop/start() to work on software events. And in fact
> now that we use the hlist_del_init, it's safe, but a bit wasteful in
> the period reset path. That's another problem that is not critical, but
> if you want to solve this by ripping the differences between software and
> hardware (which I agree with), we need a ->reset_period callback.
Why? ->start() should reprogram the hardware, so a
->stop()/poke-at-state/->start() cycle is much more flexible.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at