Messages in this thread | | | Date | Thu, 13 Jul 2017 20:04:19 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH 2/2] kernel/events: Add option to enable counting sideband events in wakeup_events |
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On 2017/07/12 12:48PM, Jiri Olsa wrote: > On Mon, Jun 19, 2017 at 08:01:08PM +0530, Naveen N. Rao wrote: > > SNIP > > > - if (!event->attr.watermark) { > > + if (!event->attr.count_sb_events && !event->attr.watermark) { > > int wakeup_events = event->attr.wakeup_events; > > > > if (wakeup_events) { > > diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c > > index 4e7c728569a8..f43a6081141f 100644 > > --- a/kernel/events/ring_buffer.c > > +++ b/kernel/events/ring_buffer.c > > @@ -197,6 +197,19 @@ __perf_output_begin(struct perf_output_handle *handle, > > * none of the data stores below can be lifted up by the compiler. > > */ > > > > + if (event->attr.count_sb_events && !event->attr.watermark) { > > + int wakeup_events = event->attr.wakeup_events; > > + > > + if (wakeup_events) { > > + int events = local_inc_return(&rb->events); > > + > > + if (events >= wakeup_events) { > > + local_sub(wakeup_events, &rb->events); > > + local_inc(&rb->wakeup); > > + } > > + } > > + } > > hum, so there's the same wakeup code in perf_output_sample, > but it's not called for non-sample (sideband) events
Good point.
> > it'd be nice to have this wakeup only once in __perf_output_begin, > but it'd change the behaviour for sideband events, which would start to > follow the wakeup_events logic.. and possibly disturb Vince's tests?
I suppose you meant 'change the behaviour for _sample_ events'. Yes, the problem with having the check here is that it will now start firing for all events, rather than just the sampling events. I am not sure if we can differentiate sample events from sideband events in __perf_output_begin(). The other aspect is also Peter's concerns around performance.
Thanks, Naveen
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