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Date: Fri, 19 Jun 2020 10:11:20 -0400
From: Phil Auld <pauld@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Qais Yousef <qais.yousef@....com>, Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Steven Rostedt <rostedt@...dmis.org>,
Juri Lelli <juri.lelli@...hat.com>,
Mel Gorman <mgorman@...e.de>
Subject: [PATCH] Sched: Add a tracepoint to track rq->nr_running
Add a bare tracepoint trace_sched_update_nr_running_tp which tracks
->nr_running CPU's rq. This is used to accurately trace this data and
provide a visualization of scheduler imbalances in, for example, the
form of a heat map. The tracepoint is accessed by loading an external
kernel module. An example module (forked from Qais' module and including
the pelt related tracepoints) can be found at:
https://github.com/auldp/tracepoints-helpers.git
A script to turn the trace-cmd report output into a heatmap plot can be
found at:
https://github.com/jirvoz/plot-nr-running
The tracepoints are added to add_nr_running() and sub_nr_running() which
are in kernel/sched/sched.h. Since sched.h includes trace/events/tlb.h
via mmu_context.h we had to limit when CREATE_TRACE_POINTS is defined.
Signed-off-by: Phil Auld <pauld@...hat.com>
CC: Qais Yousef <qais.yousef@....com>
CC: Ingo Molnar <mingo@...hat.com>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Vincent Guittot <vincent.guittot@...aro.org>
CC: linux-kernel@...r.kernel.org
---
include/trace/events/sched.h | 4 ++++
kernel/sched/core.c | 9 ++++-----
kernel/sched/fair.c | 2 --
kernel/sched/pelt.c | 2 --
kernel/sched/sched.h | 12 ++++++++++++
5 files changed, 20 insertions(+), 9 deletions(-)
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index ed168b0e2c53..a6d9fe5a68cf 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -634,6 +634,10 @@ DECLARE_TRACE(sched_overutilized_tp,
TP_PROTO(struct root_domain *rd, bool overutilized),
TP_ARGS(rd, overutilized));
+DECLARE_TRACE(sched_update_nr_running_tp,
+ TP_PROTO(int cpu, int change, unsigned int nr_running),
+ TP_ARGS(cpu, change, nr_running));
+
#endif /* _TRACE_SCHED_H */
/* This part must be outside protection */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9a2fbf98fd6f..6f28fdff1d48 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6,7 +6,10 @@
*
* Copyright (C) 1991-2002 Linus Torvalds
*/
+
+#define SCHED_CREATE_TRACE_POINTS
#include "sched.h"
+#undef SCHED_CREATE_TRACE_POINTS
#include <linux/nospec.h>
@@ -21,9 +24,6 @@
#include "pelt.h"
-#define CREATE_TRACE_POINTS
-#include <trace/events/sched.h>
-
/*
* Export tracepoints that act as a bare tracehook (ie: have no trace event
* associated with them) to allow external modules to probe them.
@@ -34,6 +34,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
@@ -7969,5 +7970,3 @@ const u32 sched_prio_to_wmult[40] = {
/* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
/* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
};
-
-#undef CREATE_TRACE_POINTS
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index da3e5b54715b..fe5d9b6db8f7 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -22,8 +22,6 @@
*/
#include "sched.h"
-#include <trace/events/sched.h>
-
/*
* Targeted preemption latency for CPU-bound tasks:
*
diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c
index b647d04d9c8b..bb69a0ae8d6c 100644
--- a/kernel/sched/pelt.c
+++ b/kernel/sched/pelt.c
@@ -28,8 +28,6 @@
#include "sched.h"
#include "pelt.h"
-#include <trace/events/sched.h>
-
/*
* Approximate:
* val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index db3a57675ccf..6ae96679c169 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -75,6 +75,15 @@
#include "cpupri.h"
#include "cpudeadline.h"
+#ifdef SCHED_CREATE_TRACE_POINTS
+#define CREATE_TRACE_POINTS
+#endif
+#include <trace/events/sched.h>
+
+#ifdef SCHED_CREATE_TRACE_POINTS
+#undef CREATE_TRACE_POINTS
+#endif
+
#ifdef CONFIG_SCHED_DEBUG
# define SCHED_WARN_ON(x) WARN_ONCE(x, #x)
#else
@@ -1959,6 +1968,7 @@ static inline void add_nr_running(struct rq *rq, unsigned count)
unsigned prev_nr = rq->nr_running;
rq->nr_running = prev_nr + count;
+ trace_sched_update_nr_running_tp(cpu_of(rq), count, rq->nr_running);
#ifdef CONFIG_SMP
if (prev_nr < 2 && rq->nr_running >= 2) {
@@ -1973,6 +1983,8 @@ static inline void add_nr_running(struct rq *rq, unsigned count)
static inline void sub_nr_running(struct rq *rq, unsigned count)
{
rq->nr_running -= count;
+ trace_sched_update_nr_running_tp(cpu_of(rq), -count, rq->nr_running);
+
/* Check if we still need preemption */
sched_update_tick_dependency(rq);
}
--
2.18.0
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