linux-kernel - Re: [PATCH] Documentation: intel_pstate: Describe hwp_dynamic

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Date:   Tue, 26 Jun 2018 16:40:27 -0700
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>
Cc:     Linux Documentation <linux-doc@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Documentation: intel_pstate: Describe hwp_dynamic_boost
 sysfs knob

On Tue, 2018-06-26 at 17:20 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Document the recently introduced hwp_dynamic_boost sysfs knob
> allowing user space to tell intel_pstate to use iowait boosting
> in the active mode with HWP enabled (to improve performance).
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>

> ---
>  Documentation/admin-guide/pm/intel_pstate.rst |   11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> Index: linux-pm/Documentation/admin-guide/pm/intel_pstate.rst
> ===================================================================
> --- linux-pm.orig/Documentation/admin-guide/pm/intel_pstate.rst
> +++ linux-pm/Documentation/admin-guide/pm/intel_pstate.rst
> @@ -378,6 +378,17 @@ argument is passed to the kernel in the
>  	but it affects the maximum possible value of per-policy P-
> state	limits
>  	(see `Interpretation of Policy Attributes`_ below for
> details).
>  
> +``hwp_dynamic_boost``
> +	This attribute is only present if ``intel_pstate`` works in
> the
> +	`active mode with the HWP feature enabled <Active Mode With
> HWP_>`_ in
> +	the processor.  If set (equal to 1), it causes the minimum
> P-state limit
> +	to be increased dynamically for a short time whenever a task
> previously
> +	waiting on I/O is selected to run on a given logical CPU
> (the purpose
> +	of this mechanism is to improve performance).
> +
> +	This setting has no effect on logical CPUs whose minimum P-
> state limit
> +	is directly set to the highest non-turbo P-state or above
> it.
> +
>  .. _status_attr:
>  
>  ``status``
>