linux-kernel - Re: [Update][PATCH v3 3/4] cpufreq: schedutil: Simplify iowait boosting

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Date:   Mon, 8 Apr 2019 11:24:45 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Quentin Perret <quentin.perret@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Chen Yu <yu.c.chen@...el.com>,
        Gabriele Mazzotta <gabriele.mzt@...il.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [Update][PATCH v3 3/4] cpufreq: schedutil: Simplify iowait
 boosting

On 28-03-19, 11:33, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> There is not reason for the minimum iowait boost value in the
> schedutil cpufreq governor to depend on the available range of CPU
> frequencies.  In fact, that dependency is generally confusing,
> because it causes the iowait boost to behave somewhat differently
> on CPUs with the same maximum frequency and different minimum
> frequencies, for example.
> 
> For this reason, replace the min field in struct sugov_cpu
> with a constant and choose its values to be 1/8 of
> SCHED_CAPACITY_SCALE (for consistency with the intel_pstate
> driver's internal governor).
> 
> [Note that policy->cpuinfo.max_freq will not be a constant any more
>  after a subsequent change, so this change is depended on by it.]
> 
> Link: https://lore.kernel.org/lkml/20190305083202.GU32494@hirez.programming.kicks-ass.net/T/#ee20bdc98b7d89f6110c0d00e5c3ee8c2ced93c3d
> Suggested-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> As pointed out by Quentin, the original patch overlooked two kerneldoc
> comments that needed to be updated along with the code, so do that here.
> 
> No other changes with respect to the original.
> 
> ---
>  kernel/sched/cpufreq_schedutil.c |   21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh