From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Linux PM <linux-pm@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC][PATCH] cpuidle: Consolidate disabled state checks
Date: Wed, 4 Sep 2019 23:54:50 +0200 [thread overview]
Message-ID: <04bde219-feea-847f-da2b-f640cd4d0476@linaro.org> (raw)
In-Reply-To: <2136682.Ujdk25Y4fk@kreacher>
Hi Rafael,
On 04/09/2019 12:41, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> There are two reasons why CPU idle states may be disabled: either
> because the driver has disabled them or because they have been
> disabled by user space via sysfs.
>
> In the former case, the state's "disabled" flag is set once during
> the initialization of the driver and it is never cleared later (it
> is read-only effectively). In the latter case, the "disable" field
> of the given state's cpuidle_state_usage struct is set and it may be
> changed via sysfs. Thus checking whether or not an idle state has
> been disabled involves reading these two flags every time.
>
> In order to avoid the additional check of the state's "disabled" flag
> (which is effectively read-only anyway), use the value of it at the
> init time to set a (new) flag in the "disable" field of that state's
> cpuidle_state_usage structure and use the sysfs interface to
> manipulate another (new) flag in it. This way the state is disabled
> whenever the "disable" field of its cpuidle_state_usage structure is
> nonzero, whatever the reason, and it is the only place to look into
> to check whether or not the state has been disabled.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>
> I have not tested this yet, hence RFC, so it is mainly for feedback.
This change makes sense.
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
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next prev parent reply other threads:[~2019-09-04 21:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-04 10:41 [RFC][PATCH] cpuidle: Consolidate disabled state checks Rafael J. Wysocki
2019-09-04 13:03 ` Peter Zijlstra
2019-09-04 21:54 ` Daniel Lezcano [this message]
2019-09-20 16:14 ` Doug Smythies
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