From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>,
mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, linux-kernel@vger.kernel.org,
tim.c.chen@linux.intel.com
Subject: Re: [PATCH 3/5] sched/fair: Wait before decaying max_newidle_lb_cost
Date: Fri, 29 Oct 2021 12:01:21 +0200 [thread overview]
Message-ID: <67218e25-a472-baa0-19bf-71af26f5e767@arm.com> (raw)
In-Reply-To: <20211019123537.17146-4-vincent.guittot@linaro.org>
On 19/10/2021 14:35, Vincent Guittot wrote:
> Decay max_newidle_lb_cost only when it has not been updated for a while
> and ensure to not decay a recently changed value.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
> include/linux/sched/topology.h | 2 +-
> kernel/sched/fair.c | 36 +++++++++++++++++++++++++---------
> kernel/sched/topology.c | 2 +-
> 3 files changed, 29 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index 2f9166f6dec8..c07bfa2d80f2 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -105,7 +105,7 @@ struct sched_domain {
>
> /* idle_balance() stats */
> u64 max_newidle_lb_cost;
> - unsigned long next_decay_max_lb_cost;
> + unsigned long last_decay_max_lb_cost;
>
> u64 avg_scan_cost; /* select_idle_sibling */
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index c4c36865321b..e50fd751e1df 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -10239,6 +10239,30 @@ void update_max_interval(void)
> max_load_balance_interval = HZ*num_online_cpus()/10;
> }
>
> +static inline bool update_newidle_cost(struct sched_domain *sd, u64 cost)
> +{
> + if (cost > sd->max_newidle_lb_cost) {
> + /*
> + * Track max cost of a domain to make sure to not delay the
> + * next wakeup on the CPU.
> + */
> + sd->max_newidle_lb_cost = cost;
> + sd->last_decay_max_lb_cost = jiffies;
That's the actual change of the patch: sd->last_decay_max_lb_cost being
moved forward also when newidle cost is updated from newidle_balance() ?
> + } else if (time_after(jiffies, sd->last_decay_max_lb_cost + HZ)) {
> + /*
> + * Decay the newidle max times by ~1% per second to ensure that
> + * it is not outdated and the current max cost is actually
> + * shorter.
I assume that `max cost` refers here to a local variable of the only
caller of update_newidle_cost(..., 0) - rebalance_domains()?
"the current max cost" has to be shorter so that
rq->max_idle_balance_cost also decays in this case. Is this what this
comment tries to say here?
[...]
next prev parent reply other threads:[~2021-10-29 10:01 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-19 12:35 [PATCH v3 0/5] Improve newidle lb cost tracking and early abort Vincent Guittot
2021-10-19 12:35 ` [PATCH v3 1/5] sched/fair: Account update_blocked_averages in newidle_balance cost Vincent Guittot
2021-10-21 9:43 ` Mel Gorman
2021-10-31 10:16 ` [tip: sched/core] " tip-bot2 for Vincent Guittot
2021-10-19 12:35 ` [PATCH v3 2/5] sched/fair: Skip update_blocked_averages if we are defering load balance Vincent Guittot
2021-10-21 9:44 ` Mel Gorman
2021-10-21 12:45 ` Vincent Guittot
2021-10-31 10:16 ` [tip: sched/core] " tip-bot2 for Vincent Guittot
2021-10-19 12:35 ` [PATCH 3/5] sched/fair: Wait before decaying max_newidle_lb_cost Vincent Guittot
2021-10-21 9:45 ` Mel Gorman
2021-10-29 10:01 ` Dietmar Eggemann [this message]
2021-10-29 12:19 ` Vincent Guittot
2021-10-31 10:16 ` [tip: sched/core] " tip-bot2 for Vincent Guittot
2021-10-19 12:35 ` [PATCH v3 4/5] sched/fair: Remove sysctl_sched_migration_cost condition Vincent Guittot
2021-10-21 9:46 ` Mel Gorman
2021-10-29 10:01 ` Dietmar Eggemann
2021-10-29 12:30 ` Vincent Guittot
2021-10-31 10:16 ` [tip: sched/core] " tip-bot2 for Vincent Guittot
2021-10-19 12:35 ` [PATCH v3 5/5] sched/fair: cleanup newidle_balance Vincent Guittot
2021-10-21 9:46 ` Mel Gorman
2021-10-31 10:16 ` [tip: sched/core] sched/fair: Cleanup newidle_balance tip-bot2 for Vincent Guittot
2021-10-21 9:52 ` [PATCH v3 0/5] Improve newidle lb cost tracking and early abort Mel Gorman
2021-10-21 12:42 ` Vincent Guittot
2021-10-26 17:25 ` Tim Chen
2021-10-27 8:49 ` Vincent Guittot
2021-10-27 20:53 ` Tim Chen
2021-10-28 12:15 ` Vincent Guittot
2021-10-28 21:36 ` Tim Chen
2021-10-29 17:00 ` Tim Chen
2021-10-31 10:18 ` Vincent Guittot
2021-10-28 23:25 ` Joel Fernandes
2021-10-29 7:49 ` Vincent Guittot
2021-10-29 19:37 ` Joel Fernandes
2021-10-29 10:01 ` Dietmar Eggemann
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