Commit 9d246053 authored by Phil Auld's avatar Phil Auld Committed by Peter Zijlstra

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. In order to avoid CREATE_TRACE_POINTS in
the header a wrapper call is used and the trace/events/sched.h include
is moved before sched.h in kernel/sched/core.
Signed-off-by: default avatarPhil Auld <pauld@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200629192303.GC120228@lorien.usersys.redhat.com
parent 07bbecb3
......@@ -2044,6 +2044,7 @@ const struct sched_avg *sched_trace_rq_avg_dl(struct rq *rq);
const struct sched_avg *sched_trace_rq_avg_irq(struct rq *rq);
int sched_trace_rq_cpu(struct rq *rq);
int sched_trace_rq_nr_running(struct rq *rq);
const struct cpumask *sched_trace_rd_span(struct root_domain *rd);
......
......@@ -642,6 +642,10 @@ DECLARE_TRACE(sched_util_est_se_tp,
TP_PROTO(struct sched_entity *se),
TP_ARGS(se));
DECLARE_TRACE(sched_update_nr_running_tp,
TP_PROTO(struct rq *rq, int change),
TP_ARGS(rq, change));
#endif /* _TRACE_SCHED_H */
/* This part must be outside protection */
......
......@@ -6,6 +6,10 @@
*
* Copyright (C) 1991-2002 Linus Torvalds
*/
#define CREATE_TRACE_POINTS
#include <trace/events/sched.h>
#undef CREATE_TRACE_POINTS
#include "sched.h"
#include <linux/nospec.h>
......@@ -23,9 +27,6 @@
#include "pelt.h"
#include "smp.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.
......@@ -38,6 +39,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp);
EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
......@@ -8195,4 +8197,7 @@ const u32 sched_prio_to_wmult[40] = {
/* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
};
#undef CREATE_TRACE_POINTS
void call_trace_sched_update_nr_running(struct rq *rq, int count)
{
trace_sched_update_nr_running_tp(rq, count);
}
......@@ -22,8 +22,6 @@
*/
#include "sched.h"
#include <trace/events/sched.h>
/*
* Targeted preemption latency for CPU-bound tasks:
*
......@@ -11296,3 +11294,9 @@ const struct cpumask *sched_trace_rd_span(struct root_domain *rd)
#endif
}
EXPORT_SYMBOL_GPL(sched_trace_rd_span);
int sched_trace_rq_nr_running(struct rq *rq)
{
return rq ? rq->nr_running : -1;
}
EXPORT_SYMBOL_GPL(sched_trace_rq_nr_running);
......@@ -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)
......
......@@ -76,6 +76,8 @@
#include "cpupri.h"
#include "cpudeadline.h"
#include <trace/events/sched.h>
#ifdef CONFIG_SCHED_DEBUG
# define SCHED_WARN_ON(x) WARN_ONCE(x, #x)
#else
......@@ -97,6 +99,7 @@ extern atomic_long_t calc_load_tasks;
extern void calc_global_load_tick(struct rq *this_rq);
extern long calc_load_fold_active(struct rq *this_rq, long adjust);
extern void call_trace_sched_update_nr_running(struct rq *rq, int count);
/*
* Helpers for converting nanosecond timing to jiffy resolution
*/
......@@ -1973,6 +1976,9 @@ static inline void add_nr_running(struct rq *rq, unsigned count)
unsigned prev_nr = rq->nr_running;
rq->nr_running = prev_nr + count;
if (trace_sched_update_nr_running_tp_enabled()) {
call_trace_sched_update_nr_running(rq, count);
}
#ifdef CONFIG_SMP
if (prev_nr < 2 && rq->nr_running >= 2) {
......@@ -1987,6 +1993,10 @@ 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;
if (trace_sched_update_nr_running_tp_enabled()) {
call_trace_sched_update_nr_running(rq, count);
}
/* Check if we still need preemption */
sched_update_tick_dependency(rq);
}
......
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