Per-thread events with a cpu filter, i.e., cpu != -1, were not reporting
correct timings when the thread never ran on the monitored cpu. The time
enabled was reported as a negative value.
This patch fixes the problem by updating tstamp_stopped, tstamp_running
in event_sched_out() for events with filters and which are marked as
INACTIVE.
The function group_sched_out() is modified to systematically call into
event_sched_out() to avoid duplicating the timing adjustment code twice.
With the patch, I now get:
$ task_cpu -i -e unhalted_core_cycles,unhalted_core_cycles noploop 2
noploop for 2 seconds
CPU0 0 unhalted_core_cycles (ena=1,991,136,594, run=0)
CPU0 0 unhalted_core_cycles (ena=1,991,136,594, run=0)
CPU1 0 unhalted_core_cycles (ena=1,991,136,594, run=0)
CPU1 0 unhalted_core_cycles (ena=1,991,136,594, run=0)
CPU2 0 unhalted_core_cycles (ena=1,991,136,594, run=0)
CPU2 0 unhalted_core_cycles (ena=1,991,136,594, run=0)
CPU3 4,747,990,931 unhalted_core_cycles (ena=1,991,136,594, run=1,991,136,594)
CPU3 4,747,990,931 unhalted_core_cycles (ena=1,991,136,594, run=1,991,136,594)
Signed-off-by: Stephane Eranian <eran...@gmail.com>
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 0d38f27..d196412 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -402,11 +402,31 @@ static void perf_group_detach(struct perf_event *event)
}
}
+static inline int
+event_filter_match(struct perf_event *event)
+{
+ return event->cpu == -1 || event->cpu == smp_processor_id();
+}
+
static void
event_sched_out(struct perf_event *event,
struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx)
{
+ u64 delta;
+ /*
+ * an event which could not be activated because of
+ * filter mismatch still needs to have its timings
+ * maintained, otherwise bogus information is return
+ * via read() for time_enabled, time_running
+ */
+ if (event->state == PERF_EVENT_STATE_INACTIVE
+ && !event_filter_match(event)) {
+ delta = ctx->time - event->tstamp_stopped;
+ event->tstamp_running += delta;
+ event->tstamp_stopped = ctx->time;
+ }
+
if (event->state != PERF_EVENT_STATE_ACTIVE)
return;
@@ -432,9 +452,7 @@ group_sched_out(struct perf_event *group_event,
struct perf_event_context *ctx)
{
struct perf_event *event;
-
- if (group_event->state != PERF_EVENT_STATE_ACTIVE)
- return;
+ int state = group_event->state;
event_sched_out(group_event, cpuctx, ctx);
@@ -444,7 +462,7 @@ group_sched_out(struct perf_event *group_event,
list_for_each_entry(event, &group_event->sibling_list, group_entry)
event_sched_out(event, cpuctx, ctx);
- if (group_event->attr.exclusive)
+ if (state == PERF_EVENT_STATE_ACTIVE && group_event->attr.exclusive)
cpuctx->exclusive = 0;
}
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