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Date: Mon, 09 Dec 2013 14:06:40 -0500
From: Rik van Riel <riel@...hat.com>
To: Mel Gorman <mgorman@...e.de>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Alex Thorlton <athorlton@....com>,
Linux-MM <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 18/18] sched: Add tracepoints related to NUMA task migration
On 12/09/2013 02:09 AM, Mel Gorman wrote:
> This patch adds three tracepoints
> o trace_sched_move_numa when a task is moved to a node
> o trace_sched_swap_numa when a task is swapped with another task
> o trace_sched_stick_numa when a numa-related migration fails
>
> The tracepoints allow the NUMA scheduler activity to be monitored and the
> following high-level metrics can be calculated
>
> o NUMA migrated stuck nr trace_sched_stick_numa
> o NUMA migrated idle nr trace_sched_move_numa
> o NUMA migrated swapped nr trace_sched_swap_numa
> o NUMA local swapped trace_sched_swap_numa src_nid == dst_nid (should never happen)
> o NUMA remote swapped trace_sched_swap_numa src_nid != dst_nid (should == NUMA migrated swapped)
> o NUMA group swapped trace_sched_swap_numa src_ngid == dst_ngid
> Maybe a small number of these are acceptable
> but a high number would be a major surprise.
> It would be even worse if bounces are frequent.
> o NUMA avg task migs. Average number of migrations for tasks
> o NUMA stddev task mig Self-explanatory
> o NUMA max task migs. Maximum number of migrations for a single task
>
> In general the intent of the tracepoints is to help diagnose problems
> where automatic NUMA balancing appears to be doing an excessive amount of
> useless work.
>
> Signed-off-by: Mel Gorman <mgorman@...e.de>
Reviewed-by: Rik van Riel <riel@...hat.com>
> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> index cf1694c..f0c54e3 100644
> --- a/include/trace/events/sched.h
> +++ b/include/trace/events/sched.h
> @@ -443,11 +443,7 @@ TRACE_EVENT(sched_process_hang,
> );
> #endif /* CONFIG_DETECT_HUNG_TASK */
>
> -/*
> - * 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_task,
> +DECLARE_EVENT_CLASS(sched_move_task_template,
>
> TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),
>
> @@ -478,6 +474,68 @@ TRACE_EVENT(sched_move_task,
> __entry->src_cpu, __entry->src_nid,
> __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_task,
> + TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),
> +
> + TP_ARGS(tsk, src_cpu, dst_cpu)
> +);
> +
> +DEFINE_EVENT(sched_move_task_template, sched_move_numa,
> + TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),
> +
> + TP_ARGS(tsk, src_cpu, 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(tsk, src_cpu, dst_cpu)
> +);
> +
> +TRACE_EVENT(sched_swap_numa,
> +
> + TP_PROTO(struct task_struct *src_tsk, int src_cpu,
> + struct task_struct *dst_tsk, int dst_cpu),
> +
> + TP_ARGS(src_tsk, src_cpu, dst_tsk, 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 = task_pid_nr(dst_tsk);
> + __entry->dst_tgid = task_tgid_nr(dst_tsk);
> + __entry->dst_ngid = task_numa_group_id(dst_tsk);
> + __entry->dst_cpu = dst_cpu;
> + __entry->dst_nid = cpu_to_node(dst_cpu);
> + ),
> +
> + 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)
> +);
> #endif /* _TRACE_SCHED_H */
>
> /* This part must be outside protection */
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index c180860..3980110 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1108,6 +1108,7 @@ int migrate_swap(struct task_struct *cur, struct task_struct *p)
> if (!cpumask_test_cpu(arg.src_cpu, tsk_cpus_allowed(arg.dst_task)))
> goto out;
>
> + trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
> ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
>
> out:
> @@ -4091,6 +4092,7 @@ int migrate_task_to(struct task_struct *p, int target_cpu)
>
> /* TODO: This is not properly updating schedstats */
>
> + trace_sched_move_numa(p, curr_cpu, target_cpu);
> return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
> }
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 41021c8..aac8c65 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -1272,11 +1272,13 @@ static int task_numa_migrate(struct task_struct *p)
> p->numa_scan_period = task_scan_min(p);
>
> if (env.best_task == NULL) {
> - int ret = migrate_task_to(p, env.best_cpu);
> + if ((ret = migrate_task_to(p, env.best_cpu)) != 0)
> + trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
> return ret;
> }
>
> - ret = migrate_swap(p, env.best_task);
> + if ((ret = migrate_swap(p, env.best_task)) != 0);
> + trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
> put_task_struct(env.best_task);
> return ret;
> }
>
--
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