linux-kernel - Re: [PATCH v4 20/24] PM / devfreq: tegra30: Optimize upper average watermark selection

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Message-ID: <20190719045943.73b53e31@dimatab>
Date:   Fri, 19 Jul 2019 04:59:43 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Chanwoo Choi <cw00.choi@...sung.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 20/24] PM / devfreq: tegra30: Optimize upper average
 watermark selection

В Fri, 19 Jul 2019 10:36:30 +0900
Chanwoo Choi <cw00.choi@...sung.com> пишет:

> On 19. 7. 8. 오전 7:32, Dmitry Osipenko wrote:
> > I noticed that CPU may be crossing the dependency threshold very
> > frequently for some workloads and this results in a lot of
> > interrupts which could be avoided if MCALL client is keeping actual
> > EMC frequency at a higher rate.
> > 
> > Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> > ---
> >  drivers/devfreq/tegra30-devfreq.c | 23 ++++++++++++++++++-----
> >  1 file changed, 18 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/devfreq/tegra30-devfreq.c
> > b/drivers/devfreq/tegra30-devfreq.c index
> > c3cf87231d25..4d582809acb6 100644 ---
> > a/drivers/devfreq/tegra30-devfreq.c +++
> > b/drivers/devfreq/tegra30-devfreq.c @@ -314,7 +314,8 @@ static void
> > tegra_actmon_get_lower_upper(struct tegra_devfreq *tegra, }
> >  
> >  static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq
> > *tegra,
> > -					   struct
> > tegra_devfreq_device *dev)
> > +					   struct
> > tegra_devfreq_device *dev,
> > +					   unsigned long freq)
> >  {
> >  	unsigned long avg_threshold, lower, upper;
> >  
> > @@ -323,6 +324,15 @@ static void
> > tegra_devfreq_update_avg_wmark(struct tegra_devfreq *tegra,
> > avg_threshold = dev->config->avg_dependency_threshold;
> > avg_threshold = avg_threshold * ACTMON_SAMPLING_PERIOD; 
> > +	/*
> > +	 * If cumulative EMC frequency selection is higher than the
> > +	 * device's, then there is no need to set upper watermark
> > to
> > +	 * a lower value because it will result in unnecessary
> > upper
> > +	 * interrupts.
> > +	 */
> > +	if (freq * ACTMON_SAMPLING_PERIOD > upper)
> > +		upper = freq * ACTMON_SAMPLING_PERIOD;  
> 
> Also, 'upper value is used on the patch5. You can combine this code
> to patch5 or if this patch depends on the cpu notifier, you can
> combine it to the patch of adding cpu notifier without separate patch.

Well okay, I'll try to squash some of the patches in the next revision.
Usually I'm receiving comments in the other direction, asking to
separate patches into smaller changes ;) So that's more a personal
preference of each maintainer, I'd say.