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

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

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

include/trace/events/sched.h

+4 −0
Original line number Diff line number Diff line
@@ -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 */

kernel/sched/core.c

+9 −4
Original line number Diff line number Diff line
@@ -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);

}

kernel/sched/fair.c

+6 −2
Original line number Diff line number Diff line
@@ -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);

kernel/sched/pelt.c

+0 −2
Original line number Diff line number Diff line
@@ -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)

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