[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <cfc3de8fa3172cedf406ccef8c94ef4da0a00281.camel@linux.intel.com>
Date: Tue, 05 Sep 2023 13:28:21 -0700
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
Valentin Schneider <vschneid@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Juri Lelli <juri.lelli@...hat.com>,
Swapnil Sapkal <Swapnil.Sapkal@....com>,
Aaron Lu <aaron.lu@...el.com>,
Julien Desfossez <jdesfossez@...italocean.com>, x86@...nel.org
Subject: Re: [RFC PATCH 1/2] sched: Rate limit migrations to 1 per 2ms per
task
On Tue, 2023-09-05 at 13:11 -0400, Mathieu Desnoyers wrote:
> Rate limit migrations to 1 migration per 2 milliseconds per task. On a
> kernel with EEVDF scheduler (commit b97d64c722598ffed42ece814a2cb791336c6679),
> this speeds up hackbench from 62s to 45s on AMD EPYC 192-core (over 2 sockets).
>
>
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 479db611f46e..0d294fce261d 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4510,6 +4510,7 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
> p->se.vruntime = 0;
> p->se.vlag = 0;
> p->se.slice = sysctl_sched_base_slice;
> + p->se.next_migration_time = 0;
It seems like the next_migration_time should be initialized to the current time,
in case the system run for a long time and clock wrap around could cause problem.
> INIT_LIST_HEAD(&p->se.group_node);
>
> #ifdef CONFIG_FAIR_GROUP_SCHED
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index d92da2d78774..24ac69913005 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -960,6 +960,14 @@ int sched_update_scaling(void)
>
> static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se);
>
> +static bool should_migrate_task(struct task_struct *p, int prev_cpu)
> +{
> + /* Rate limit task migration. */
> + if (sched_clock_cpu(prev_cpu) < p->se.next_migration_time)
Should we use time_before(sched_clock_cpu(prev_cpu), p->se.next_migration_time) ?
> + return false;
> + return true;
> +}
> +
Thanks.
Tim
Powered by blists - more mailing lists