Remote wakeups of polling CPUs are a valuable performance
improvement; add a tracepoint to make it much easier to verify that
they're working.
Signed-off-by: Andy Lutomirski <l...@amacapital.net>
---
include/trace/events/sched.h | 20 ++++++++++++++++++++
kernel/sched/core.c | 4 ++++
2 files changed, 24 insertions(+)
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 67e1bbf..08f8632 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -530,6 +530,26 @@ TRACE_EVENT(sched_swap_numa,
__entry->dst_pid, __entry->dst_tgid, __entry->dst_ngid,
__entry->dst_cpu, __entry->dst_nid)
);
+
+/*
+ * Tracepoint for waking a polling cpu without an IPI.
+ */
+TRACE_EVENT(sched_wake_polling_cpu,
+
+ TP_PROTO(int cpu),
+
+ TP_ARGS(cpu),
+
+ TP_STRUCT__entry(
+ __field( int, cpu )
+ ),
+
+ TP_fast_assign(
+ __entry->cpu = cpu;
+ ),
+
+ TP_printk("cpu=%d", __entry->cpu)
+);
#endif /* _TRACE_SCHED_H */
/* This part must be outside protection */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 321d800..18bebfc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -564,6 +564,8 @@ void resched_task(struct task_struct *p)
if (set_nr_and_not_polling(p))
smp_send_reschedule(cpu);
+ else
+ trace_sched_wake_polling_cpu(cpu);
}
void resched_cpu(int cpu)
@@ -647,6 +649,8 @@ static void wake_up_idle_cpu(int cpu)
smp_mb();
if (!tsk_is_polling(rq->idle))
smp_send_reschedule(cpu);
+ else
+ trace_sched_wake_polling_cpu(cpu);
}
static bool wake_up_full_nohz_cpu(int cpu)
--
1.9.3
--
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