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

[Frederic Weisbecker <fweisbec@gmail.com>]

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.