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    SubjectRe: [PATCH v2] 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: Phil Auld <pauld@redhat.com>
    CC: Qais Yousef <qais.yousef@arm.com>
    CC: Ingo Molnar <mingo@redhat.com>
    CC: Peter Zijlstra <peterz@infradead.org>
    CC: Vincent Guittot <vincent.guittot@linaro.org>
    CC: Steven Rostedt <rostedt@goodmis.org>
    CC: linux-kernel@vger.kernel.org
    ---

    V2: Fix use of tracepoint in header from Steven. Pass rq* and use
    helper to get nr_running field, from Qais.


    include/linux/sched.h | 1 +
    include/trace/events/sched.h | 4 ++++
    kernel/sched/core.c | 13 +++++++++----
    kernel/sched/fair.c | 8 ++++++--
    kernel/sched/pelt.c | 2 --
    kernel/sched/sched.h | 10 ++++++++++
    6 files changed, 30 insertions(+), 8 deletions(-)

    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index 4418f5cb8324..5f114faf2247 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -2015,6 +2015,7 @@ 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);

    diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
    index ed168b0e2c53..8c72f9113694 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(struct rq *rq, int change),
    + TP_ARGS(rq, change));
    +
    #endif /* _TRACE_SCHED_H */

    /* This part must be outside protection */
    diff --git a/kernel/sched/core.c b/kernel/sched/core.c
    index 9a2fbf98fd6f..0d35d7c4c330 100644
    --- a/kernel/sched/core.c
    +++ b/kernel/sched/core.c
    @@ -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>
    @@ -21,9 +25,6 @@

    #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 +35,7 @@ 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);

    @@ -7970,4 +7972,7 @@ 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);
    +}
    diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
    index da3e5b54715b..2e2f3f68e318 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:
    *
    @@ -11293,3 +11291,9 @@ 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);
    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..e621eaa44474 100644
    --- a/kernel/sched/sched.h
    +++ b/kernel/sched/sched.h
    @@ -75,6 +75,8 @@
    #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
    @@ -96,6 +98,7 @@ 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
    */
    @@ -1959,6 +1962,9 @@ 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) {
    @@ -1973,6 +1979,10 @@ 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);
    }
    --
    2.18.0

    --

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