From: Peter Zijlstra <peterz@infradead.org>
To: Carlos Bilbao <carlos.bilbao@amd.com>
Cc: juri.lelli@redhat.com, vincent.guittot@linaro.org,
mingo@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kernel/sched: Update schedstats when migrating threads
Date: Wed, 23 Feb 2022 11:19:27 +0100 [thread overview]
Message-ID: <YhYKL4hxx4TNKHGD@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20220126152222.5429-1-carlos.bilbao@amd.com>
On Wed, Jan 26, 2022 at 09:22:23AM -0600, Carlos Bilbao wrote:
> The kernel manages per-task scheduler statistics or schedstats. Such
> counters should be reinitialized when the thread is migrated to a
> different core rq, except for the values recording number of migrations.
I'm confused, why should we reset schedstats on migrate? I'm thinking
this breaks per-task, since tasks tend to bounce around quite a lot.
> Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>
> ---
> kernel/sched/core.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index fe53e510e711..d64c2a290176 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8757,6 +8757,7 @@ bool sched_smp_initialized __read_mostly;
> int migrate_task_to(struct task_struct *p, int target_cpu)
> {
> struct migration_arg arg = { p, target_cpu };
> + uint64_t forced_migrations, migrations_cold;
> int curr_cpu = task_cpu(p);
>
> if (curr_cpu == target_cpu)
> @@ -8765,7 +8766,14 @@ int migrate_task_to(struct task_struct *p, int target_cpu)
> if (!cpumask_test_cpu(target_cpu, p->cpus_ptr))
> return -EINVAL;
>
> - /* TODO: This is not properly updating schedstats */
> + if (schedstat_enabled()) {
> + forced_migrations = schedstat_val(p->stats.nr_forced_migrations);
> + migrations_cold = schedstat_val(p->stats.nr_migrations_cold);
> + memset(&p->stats, 0, sizeof(p->stats));
> + schedstat_set(p->stats.nr_forced_migrations, forced_migrations);
> + schedstat_set(p->stats.nr_migrations_cold, migrations_cold);
> + schedstat_inc(p->stats.nr_migrations_cold);
> + }
>
> trace_sched_move_numa(p, curr_cpu, target_cpu);
> return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
> --
> 2.27.0
>
next prev parent reply other threads:[~2022-02-23 10:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-26 15:22 [PATCH] kernel/sched: Update schedstats when migrating threads Carlos Bilbao
2022-02-22 16:32 ` Carlos Bilbao
2022-02-22 17:15 ` Steven Rostedt
2022-02-23 10:19 ` Peter Zijlstra [this message]
2022-02-23 15:14 ` Carlos Bilbao
2022-02-23 15:28 ` Phil Auld
2022-02-23 15:33 ` Carlos Bilbao
2022-02-23 15:47 ` Phil Auld
2022-02-23 15:59 ` Carlos Bilbao
2022-02-23 16:13 ` [PATCH v2] " Carlos Bilbao
2022-02-24 14:03 ` Phil Auld
2022-02-24 15:05 ` Carlos Bilbao
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