perf/core: Add group reads to perf_event_read()

Enable perf_event_read() to update entire groups at once, this will be
useful for read transactions.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20150723080435.GE25159@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 32 insertions, 7 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 67b7dba4f0b5..4d89866edd4e 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3184,12 +3184,18 @@ void perf_event_exec(void)
         rcu_read_unlock();
 }
 
+struct perf_read_data {
+        struct perf_event *event;
+        bool group;
+};
+
 /*
  * Cross CPU call to read the hardware event
  */
 static void __perf_event_read(void *info)
 {
-        struct perf_event *event = info;
+        struct perf_read_data *data = info;
+        struct perf_event *sub, *event = data->event;
         struct perf_event_context *ctx = event->ctx;
         struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
 
@@ -3208,9 +3214,21 @@ static void __perf_event_read(void *info)
                 update_context_time(ctx);
                 update_cgrp_time_from_event(event);
         }
+
         update_event_times(event);
         if (event->state == PERF_EVENT_STATE_ACTIVE)
                 event->pmu->read(event);
+
+        if (!data->group)
+                goto unlock;
+
+        list_for_each_entry(sub, &event->sibling_list, group_entry) {
+                update_event_times(sub);
+                if (sub->state == PERF_EVENT_STATE_ACTIVE)
+                        sub->pmu->read(sub);
+        }
+
+unlock:
         raw_spin_unlock(&ctx->lock);
 }
 
@@ -3275,15 +3293,19 @@ u64 perf_event_read_local(struct perf_event *event)
         return val;
 }
 
-static void perf_event_read(struct perf_event *event)
+static void perf_event_read(struct perf_event *event, bool group)
 {
         /*
          * If event is enabled and currently active on a CPU, update the
          * value in the event structure:
          */
         if (event->state == PERF_EVENT_STATE_ACTIVE) {
+                struct perf_read_data data = {
+                        .event = event,
+                        .group = group,
+                };
                 smp_call_function_single(event->oncpu,
-                                         __perf_event_read, event, 1);
+                                         __perf_event_read, &data, 1);
         } else if (event->state == PERF_EVENT_STATE_INACTIVE) {
                 struct perf_event_context *ctx = event->ctx;
                 unsigned long flags;
@@ -3298,7 +3320,10 @@ static void perf_event_read(struct perf_event *event)
                         update_context_time(ctx);
                         update_cgrp_time_from_event(event);
                 }
-                update_event_times(event);
+                if (group)
+                        update_group_times(event);
+                else
+                        update_event_times(event);
                 raw_spin_unlock_irqrestore(&ctx->lock, flags);
         }
 }
@@ -3817,7 +3842,7 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
 
         mutex_lock(&event->child_mutex);
 
-        perf_event_read(event);
+        perf_event_read(event, false);
         total += perf_event_count(event);
 
         *enabled += event->total_time_enabled +
@@ -3826,7 +3851,7 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
                         atomic64_read(&event->child_total_time_running);
 
         list_for_each_entry(child, &event->child_list, child_list) {
-                perf_event_read(child);
+                perf_event_read(child, false);
                 total += perf_event_count(child);
                 *enabled += child->total_time_enabled;
                 *running += child->total_time_running;
@@ -3987,7 +4012,7 @@ static unsigned int perf_poll(struct file *file, poll_table *wait)
 
 static void _perf_event_reset(struct perf_event *event)
 {
-        perf_event_read(event);
+        perf_event_read(event, false);
         local64_set(&event->count, 0);
         perf_event_update_userpage(event);
 }