perf: Multiple task contexts

Provide the infrastructure for multiple task contexts.

A more flexible approach would have resulted in more pointer chases
in the scheduling hot-paths. This approach has the limitation of a
static number of task contexts.

Since I expect most external PMUs to be system wide, or at least node
wide (as per the intel uncore unit) they won't actually need a task
context.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: paulus <paulus@samba.org>
Cc: stephane eranian <eranian@googlemail.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Lin Ming <ming.m.lin@intel.com>
Cc: Yanmin <yanmin_zhang@linux.intel.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 8 insertions, 1 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 22155ef3b362..9ecfd856ce6e 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -572,6 +572,7 @@ struct pmu {
 
         int * __percpu                  pmu_disable_count;
         struct perf_cpu_context * __percpu pmu_cpu_context;
+        int                             task_ctx_nr;
 
         /*
          * Fully disable/enable this PMU, can be used to protect from the PMI
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1e2a6db2d7dd..89d6023c6f82 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1160,6 +1160,12 @@ struct sched_rt_entity {
 
 struct rcu_node;
 
+enum perf_event_task_context {
+        perf_invalid_context = -1,
+        perf_hw_context = 0,
+        perf_nr_task_contexts,
+};
+
 struct task_struct {
         volatile long state;    /* -1 unrunnable, 0 runnable, >0 stopped */
         void *stack;
@@ -1431,7 +1437,7 @@ struct task_struct {
         struct futex_pi_state *pi_state_cache;
 #endif
 #ifdef CONFIG_PERF_EVENTS
-        struct perf_event_context *perf_event_ctxp;
+        struct perf_event_context *perf_event_ctxp[perf_nr_task_contexts];
         struct mutex perf_event_mutex;
         struct list_head perf_event_list;
 #endif