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[PATCH 19/32] perf/core: introduce PMU event flag PERF_CGROUP_NO_RECURSION

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Some events, such as Intel's CQM llc_occupancy, need small deviations
from the traditional behavior in the generic code in a way that depends
on the event itself (and known by the PMU) and not in a field of
perf_event_attrs.

An example is the recursive scope for cgroups: The generic code handles
cgroup hierarchy for a cgroup C by simultaneously adding to the PMU
the events of all cgroups that are ancestors of C. This approach is
incompatible with the CQM hw that only allows one RMID per virtual core
at a time. CQM's PMU work-arounds this limitation by internally
maintaining the hierarchical dependency between monitored cgroups and
only requires that the generic code adds current cgroup's event to
the PMU.

The introduction of the flag PERF_CGROUP_NO_RECURSION allows the PMU to
signal the generic code to avoid using recursive cgroup scope for
llc_occupancy events, preventing an undesired overwrite of RMIDs.

The PERF_CGROUP_NO_RECURSION, introduced in this patch, is the first flag
of this type, more will be added in this patch series.
To keep things tidy, this patch introduces the flag field pmu_event_flag,
intended to contain all flags that:
  - Are not user-configurable event attributes (not suitable for
    perf_event_attributes).
  - Are known by the PMU during initialization of struct perf_event.
  - Signal something to the generic code.

Reviewed-by: Stephane Eranian <eranian@google.com>
Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
 include/linux/perf_event.h | 10 ++++++++++
 kernel/events/core.c       |  3 +++
 2 files changed, 13 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 81e29c6..e4c58b0 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -594,9 +594,19 @@ struct perf_event {
 #endif
 
 	struct list_head		sb_list;
+
+	/* Flags to generic code set by PMU. */
+	int				pmu_event_flags;
+
 #endif /* CONFIG_PERF_EVENTS */
 };
 
+/*
+ * Possible flags for mpu_event_flags.
+ */
+/* Do not enable cgroup events in descendant cgroups. */
+#define PERF_CGROUP_NO_RECURSION		(1 << 0)
+
 /**
  * struct perf_event_context - event context structure
  *
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2a868a6..33961ec 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -545,6 +545,9 @@ perf_cgroup_match(struct perf_event *event)
 	if (!cpuctx->cgrp)
 		return false;
 
+	if (event->pmu_event_flags & PERF_CGROUP_NO_RECURSION)
+		return cpuctx->cgrp->css.cgroup == event->cgrp->css.cgroup;
+
 	/*
 	 * Cgroup scoping is recursive.  An event enabled for a cgroup is
 	 * also enabled for all its descendant cgroups.  If @cpuctx's
-- 
2.8.0.rc3.226.g39d4020

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[PATCH 00/32] 2nd Iteration of Cache QoS Monitoring support. David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 06:50 +0200
  [PATCH 01/32] perf/x86/intel/cqm: temporarily remove MBM from CQM and cleanup David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 06:50 +0200
    Re: [PATCH 01/32] perf/x86/intel/cqm: temporarily remove MBM from  CQM and cleanup Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2016-04-29 22:30 +0200
  [PATCH 24/32] perf/x86/intel/cqm: use PERF_INACTIVE_*_READ_* flags in CQM David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 06:50 +0200
  [PATCH 25/32] sched: introduce the finish_arch_pre_lock_switch() scheduler hook David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 06:50 +0200
    Re: [PATCH 25/32] sched: introduce the finish_arch_pre_lock_switch()  scheduler hook Peter Zijlstra <peterz@infradead.org> - 2016-04-29 11:00 +0200
      Re: [PATCH 25/32] sched: introduce the finish_arch_pre_lock_switch()  scheduler hook David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 20:50 +0200
        Re: [PATCH 25/32] sched: introduce the finish_arch_pre_lock_switch()  scheduler hook Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2016-04-29 22:30 +0200
          Re: [PATCH 25/32] sched: introduce the finish_arch_pre_lock_switch()  scheduler hook David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 23:00 +0200
  [PATCH 14/32] perf/x86/intel/cqm: add preallocation of anodes David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 06:50 +0200
  [PATCH 32/32] perf/stat: revamp error handling for snapshot and per_pkg events David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 06:50 +0200
  [PATCH 09/32] perf/x86/intel/cqm: add per-package RMIDs, data and locks David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 06:50 +0200
    Re: [PATCH 09/32] perf/x86/intel/cqm: add per-package RMIDs, data  and locks Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2016-04-29 23:00 +0200
  [PATCH 29/32] perf,perf/x86,perf/powerpc,perf/arm,perf/*: add int error return to pmu::read David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 06:50 +0200
  [PATCH 06/32] x86/intel,cqm: add CONFIG_INTEL_RDT configuration flag and refactor PQR David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 06:50 +0200
  [PATCH 15/32] perf/core: add hooks to expose architecture specific features in perf_cgroup David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  [PATCH 18/32] perf/x86/intel/cqm: use pmu::event_terminate David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  [PATCH 16/32] perf/x86/intel/cqm: add cgroup support David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  [PATCH 17/32] perf/core: adding pmu::event_terminate David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  [PATCH 05/32] perf/core: remove unused pmu->count David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  [PATCH 04/32] perf/x86/intel/cqm: make read of RMIDs per package (Temporal) David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  [PATCH 11/32] perf/x86/intel/cqm: (I)state and limbo prmids David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  [PATCH 12/32] perf/x86/intel/cqm: add per-package RMID rotation David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  [PATCH 08/32] perf/x86/intel/cqm: prepare for next patches David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
    Re: [PATCH 08/32] perf/x86/intel/cqm: prepare for next patches Peter Zijlstra <peterz@infradead.org> - 2016-04-29 11:20 +0200
  [PATCH 07/32] perf/x86/intel/cqm: separate CQM PMU's attributes from x86 PMU David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  [PATCH 19/32] perf/core: introduce PMU event flag PERF_CGROUP_NO_RECURSION David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  [PATCH 10/32] perf/x86/intel/cqm: basic RMID hierarchy with per package rmids David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 07:00 +0200
  Re: [PATCH 00/32] 2nd Iteration of Cache QoS Monitoring support. Vikas Shivappa <vikas.shivappa@linux.intel.com> - 2016-04-29 23:10 +0200
    Re: [PATCH 00/32] 2nd Iteration of Cache QoS Monitoring support. David Carrillo-Cisneros <davidcc@google.com> - 2016-04-29 23:20 +0200

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