From: Sudeep Holla <sudeep.holla@arm•com>
To: Linus Walleij <linus.walleij@linaro•org>
Cc: Arnd Bergmann <arnd@arndb•de>,
linux-pm@vger•kernel.org, Viresh Kumar <viresh.kumar@linaro•org>,
"Rafael J . Wysocki" <rafael@kernel•org>,
Russell King <linux@armlinux•org.uk>,
Sudeep Holla <sudeep.holla@arm•com>,
linux-arm-kernel@lists•infradead.org
Subject: Re: [PATCH] cpufreq: Select schedutil when using big.LITTLE
Date: Thu, 2 Apr 2020 10:14:55 +0100 [thread overview]
Message-ID: <20200402091446.GA19366@bogus> (raw)
In-Reply-To: <20200402080239.7471-1-linus.walleij@linaro.org>
On Thu, Apr 02, 2020 at 10:02:39AM +0200, Linus Walleij wrote:
> When we are using a system with big.LITTLE HMP
> configuration, we need to use EAS to schedule the
> system.
>
> As can be seen from kernel/sched/topology.c:
>
> "EAS can be used on a root domain if it meets all the following conditions:
> 1. an Energy Model (EM) is available;
> 2. the SD_ASYM_CPUCAPACITY flag is set in the sched_domain hierarchy.
> 3. no SMT is detected.
> 4. the EM complexity is low enough to keep scheduling overheads low;
> 5. schedutil is driving the frequency of all CPUs of the rd;"
>
> This means that at the very least, schedutil needs to be
> available as a scheduling policy for EAS to work on these
> systems. Make this explicit by defaulting to the schedutil
> governor if BIG_LITTLE is selected.
>
> Currently users of the TC2 board (like me) has to figure these
> dependencies out themselves and it is not helpful.
>
> Suggested-by: Arnd Bergmann <arnd@arndb•de>
> Cc: Vincent Guittot <vincent.guittot@linaro•org>
> Cc: Viresh Kumar <viresh.kumar@linaro•org>
> Cc: Sudeep Holla <sudeep.holla@arm•com>
Good to see another user of TC2 ;)
FWIW:
Acked-by: Sudeep Holla <sudeep.holla@arm•com>
--
Regards,
Sudeep
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next prev parent reply other threads:[~2020-04-02 9:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-02 8:02 [PATCH] cpufreq: Select schedutil when using big.LITTLE Linus Walleij
2020-04-02 9:14 ` Sudeep Holla [this message]
2020-04-02 9:44 ` Rafael J. Wysocki
2020-04-03 5:48 ` Viresh Kumar
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