[PATCH v3 08/11] sched_ext: Add an event, SCX_EV_BYPASS_DURATION

[Changwoo Min <changwoo@igalia.com>]

Add a core event, SCX_EV_BYPASS_DURATION, which represents the
total duration of bypass modes in nanoseconds.

Signed-off-by: Changwoo Min <changwoo@igalia.com>
---
 kernel/sched/ext.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 236cdb0071eb..b4871409bd1c 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -1468,6 +1468,11 @@ struct scx_event_stats {
 	 */
 	u64		SCX_EV_ENQ_SKIP_EXITING;
 
+	/*
+	 * The total duration of bypass modes in nanoseconds.
+	 */
+	u64		SCX_EV_BYPASS_DURATION;
+
 	/*
 	 * The number of tasks dispatched in the bypassing mode.
 	 */
@@ -1529,6 +1534,12 @@ static DEFINE_PER_CPU(struct scx_event_stats, event_stats_cpu);
 } while (0)
 
 
+/*
+ * The last time the bypass mode started.
+ * This is used to measure SCX_EV_BYPASS_DURATION.
+ */
+static unsigned long scx_bypass_timestamp;
+
 static void scx_bpf_events(struct scx_event_stats *events, size_t events__sz);
 
 static enum scx_ops_enable_state scx_ops_enable_state(void)
@@ -4422,12 +4433,15 @@ static void scx_ops_bypass(bool bypass)
 		WARN_ON_ONCE(scx_ops_bypass_depth <= 0);
 		if (scx_ops_bypass_depth != 1)
 			goto unlock;
+		scx_bypass_timestamp = ktime_get_ns();
 		scx_add_event(SCX_EV_BYPASS_ACTIVATE, 1);
 	} else {
 		scx_ops_bypass_depth--;
 		WARN_ON_ONCE(scx_ops_bypass_depth < 0);
 		if (scx_ops_bypass_depth != 0)
 			goto unlock;
+		scx_add_event(SCX_EV_BYPASS_DURATION,
+			      ktime_get_ns() - scx_bypass_timestamp);
 	}
 
 	atomic_inc(&scx_ops_breather_depth);
@@ -5018,6 +5032,7 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
 	scx_dump_event(s, &events, SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE);
 	scx_dump_event(s, &events, SCX_EV_DISPATCH_KEEP_LAST);
 	scx_dump_event(s, &events, SCX_EV_ENQ_SKIP_EXITING);
+	scx_dump_event(s, &events, SCX_EV_BYPASS_DURATION);
 	scx_dump_event(s, &events, SCX_EV_BYPASS_DISPATCH);
 	scx_dump_event(s, &events, SCX_EV_BYPASS_ACTIVATE);
 
@@ -7156,6 +7171,7 @@ __bpf_kfunc void scx_bpf_events(struct scx_event_stats *events,
 		scx_agg_event(&e_sys, e_cpu, SCX_EV_SELECT_CPU_FALLBACK);
 		scx_agg_event(&e_sys, e_cpu, SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE);
 		scx_agg_event(&e_sys, e_cpu, SCX_EV_DISPATCH_KEEP_LAST);
+		scx_agg_event(&e_sys, e_cpu, SCX_EV_BYPASS_DURATION);
 		scx_agg_event(&e_sys, e_cpu, SCX_EV_BYPASS_DISPATCH);
 		scx_agg_event(&e_sys, e_cpu, SCX_EV_BYPASS_ACTIVATE);
 	}
-- 
2.48.1