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SubjectRe: [PATCH 05/11] sched/numa: Distinguish between the different task_numa_migrate failure cases
On Wed, 12 Feb 2020 09:36:48 +0000
Mel Gorman <mgorman@techsingularity.net> wrote:

> sched:sched_stick_numa is meant to fire when a task is unable to migrate
> to the preferred node but from the trace, it's possibile to tell the
> difference between "no CPU found", "migration to idle CPU failed" and
> "tasks could not be swapped". Extend the tracepoint accordingly.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> ---
> include/trace/events/sched.h | 51 +++++++++++++++++++++++++++++++++-----------
> kernel/sched/fair.c | 6 +++---
> 2 files changed, 42 insertions(+), 15 deletions(-)
>
> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> index 420e80e56e55..3d07c0af4ab8 100644
> --- a/include/trace/events/sched.h
> +++ b/include/trace/events/sched.h
> @@ -487,7 +487,11 @@ TRACE_EVENT(sched_process_hang,
> );
> #endif /* CONFIG_DETECT_HUNG_TASK */
>
> -DECLARE_EVENT_CLASS(sched_move_task_template,
> +/*
> + * Tracks migration of tasks from one runqueue to another. Can be used to
> + * detect if automatic NUMA balancing is bouncing between nodes
> + */
> +TRACE_EVENT(sched_move_numa,
>
> TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),
>
> @@ -519,20 +523,43 @@ DECLARE_EVENT_CLASS(sched_move_task_template,
> __entry->dst_cpu, __entry->dst_nid)
> );
>
> -/*
> - * Tracks migration of tasks from one runqueue to another. Can be used to
> - * detect if automatic NUMA balancing is bouncing between nodes
> - */
> -DEFINE_EVENT(sched_move_task_template, sched_move_numa,
> - TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),
> +TRACE_EVENT(sched_stick_numa,
>
> - TP_ARGS(tsk, src_cpu, dst_cpu)
> -);
> + TP_PROTO(struct task_struct *src_tsk, int src_cpu, struct task_struct *dst_tsk, int dst_cpu),
>
> -DEFINE_EVENT(sched_move_task_template, sched_stick_numa,
> - TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),
> + TP_ARGS(src_tsk, src_cpu, dst_tsk, dst_cpu),
>
> - TP_ARGS(tsk, src_cpu, dst_cpu)
> + TP_STRUCT__entry(
> + __field( pid_t, src_pid )
> + __field( pid_t, src_tgid )
> + __field( pid_t, src_ngid )
> + __field( int, src_cpu )
> + __field( int, src_nid )
> + __field( pid_t, dst_pid )
> + __field( pid_t, dst_tgid )
> + __field( pid_t, dst_ngid )
> + __field( int, dst_cpu )
> + __field( int, dst_nid )
> + ),
> +
> + TP_fast_assign(
> + __entry->src_pid = task_pid_nr(src_tsk);
> + __entry->src_tgid = task_tgid_nr(src_tsk);
> + __entry->src_ngid = task_numa_group_id(src_tsk);
> + __entry->src_cpu = src_cpu;
> + __entry->src_nid = cpu_to_node(src_cpu);
> + __entry->dst_pid = dst_tsk ? task_pid_nr(dst_tsk) : 0;
> + __entry->dst_tgid = dst_tsk ? task_tgid_nr(dst_tsk) : 0;
> + __entry->dst_ngid = dst_tsk ? task_numa_group_id(dst_tsk) : 0;
> + __entry->dst_cpu = dst_cpu;
> + __entry->dst_nid = dst_cpu >= 0 ? cpu_to_node(dst_cpu) : -1;
> + ),
> +
> + TP_printk("src_pid=%d src_tgid=%d src_ngid=%d src_cpu=%d src_nid=%d dst_pid=%d dst_tgid=%d dst_ngid=%d dst_cpu=%d dst_nid=%d",
> + __entry->src_pid, __entry->src_tgid, __entry->src_ngid,
> + __entry->src_cpu, __entry->src_nid,
> + __entry->dst_pid, __entry->dst_tgid, __entry->dst_ngid,
> + __entry->dst_cpu, __entry->dst_nid)
> );
>

The above looks the same as the below sched_swap_numa. Can you make a
DECLARE_EVENT_CLASS() and merge the two for sched_swap_numa?

Note, most the footprint of a trace event happens in the
DECLARE_EVENT_CLASS() (a TRACE_EVENT() is just a DECLARE_EVENT_CLASS()
and DEFINE_EVENT() put together). The more DECLARE_EVENT_CLASS()s you
can share, the less the footprint is.

-- Steve


> TRACE_EVENT(sched_swap_numa,
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 4ab18fba5b82..6005ce28033b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -1849,7 +1849,7 @@ static int task_numa_migrate(struct task_struct *p)
>
> /* No better CPU than the current one was found. */
> if (env.best_cpu == -1) {
> - trace_sched_stick_numa(p, env.src_cpu, -1);
> + trace_sched_stick_numa(p, env.src_cpu, NULL, -1);
> return -EAGAIN;
> }
>
> @@ -1858,7 +1858,7 @@ static int task_numa_migrate(struct task_struct *p)
> ret = migrate_task_to(p, env.best_cpu);
> WRITE_ONCE(best_rq->numa_migrate_on, 0);
> if (ret != 0)
> - trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
> + trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu);
> return ret;
> }
>
> @@ -1866,7 +1866,7 @@ static int task_numa_migrate(struct task_struct *p)
> WRITE_ONCE(best_rq->numa_migrate_on, 0);
>
> if (ret != 0)
> - trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
> + trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu);
> put_task_struct(env.best_task);
> return ret;
> }

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