Messages in this thread |  | | Date | Fri, 10 Oct 2014 12:54:25 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 10/11] perf/x86/intel: Support task events with Intel CQM |
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On Wed, Oct 08, 2014 at 01:07:43PM +0200, Peter Zijlstra wrote: > On Wed, Sep 24, 2014 at 03:04:14PM +0100, Matt Fleming wrote: > > From: Matt Fleming <matt.fleming@intel.com> > > > > Add support for task events as well as system-wide events. This change > > has a big impact on the way that we gather LLC occupancy values in > > intel_cqm_event_read(). > > > > Currently, for system-wide (per-cpu) events we defer processing to > > userspace which knows how to discard all but one cpu result per package. > > > > Things aren't so simple for task events because we need to do the value > > aggregation ourselves. To do this, we defer updating the LLC occupancy > > value in event->count from intel_cqm_event_read() and do an SMP > > cross-call to read values for all packages in intel_cqm_event_count(). > > We need to ensure that we only do this for one task event per cache > > group, otherwise we'll report duplicate values. > > > > If we're a system-wide event we want to fallback to the default > > perf_event_count() implementation. Refactor this into a common function > > so that we don't duplicate the code. > > So it looks like these events will be classified as regular HW events, > this means they'll be mixed with the other HW events, and we'll stop > scheduling the moment either one returns a fail. > > There are two alternatives; > 1) create an extra task context to keep them in > 2) pretend to be a software event and do the scheduling yourself > > I think my initial proposal was 2, can you clarify why you've changed > that? Lemme go read the next patch though, maybe that'll clarify things > further.
As you rightly pointed out on IRC, the following (as found in patch 8):
+static struct pmu intel_cqm_pmu = { + .attr_groups = intel_cqm_attr_groups, + .task_ctx_nr = perf_sw_context,
Does indeed make it a software event, so then need to do all the scheduling outselves.
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