[tip:sched/core] sched, trace: Add a tracepoint for IPI-less remote wakeups

tip-bot for Andy Lutomirski
2014-06-05T14:38:39Z

Commit-ID: dfc68f29ae67f2a6e799b44e6a4eb3417dffbfcd
Gitweb: http://git.kernel.org/tip/dfc68f29ae67f2a6e799b44e6a4eb3417dffbfcd
Author: Andy Lutomirski <luto@amacapital.net>
AuthorDate: Wed, 4 Jun 2014 10:31:15 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 5 Jun 2014 12:09:50 +0200

sched, trace: Add a tracepoint for IPI-less remote wakeups

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 <luto@amacapital.net>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: nicolas.pitre@linaro.org
Cc: daniel.lezcano@linaro.org
Cc: umgwanakikbuti@gmail.com
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/16205aee116772aa686814f9b13bccb562108047.1401902905.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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..0a68d5a 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_idle_without_ipi,
+
+ 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 5976ca5..e4c0ddd 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_idle_without_ipi(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_idle_without_ipi(cpu);
}

static bool wake_up_full_nohz_cpu(int cpu)