linux-kernel - Re: [PATCH] thermal: sysfs: fall back to vzalloc for cooling device's statistics

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Date:   Wed, 26 Aug 2020 10:13:19 +0800
From:   Yue Hu <zbestahu@...il.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     rui.zhang@...el.com, amit.kucheria@...durent.com,
        viresh.kumar@...aro.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, huyue2@...ong.com, zbestahu@....com
Subject: Re: [PATCH] thermal: sysfs: fall back to vzalloc for cooling
 device's statistics

On Mon, 24 Aug 2020 12:40:35 +0200
Daniel Lezcano <daniel.lezcano@...aro.org> wrote:

> On 18/08/2020 08:30, Yue Hu wrote:
> > From: Yue Hu <huyue2@...ong.com>
> > 
> > We observed warning about kzalloc() when register thermal cooling device
> > in backlight_device_register(). backlight display can be a cooling device
> > since reducing screen brightness will can help reduce temperature.
> > 
> > However, ->get_max_state of backlight will assign max brightness of 1024
> > to states. The memory size can be getting 1MB+ due to states * states.  
> 
> What are the benefits of a 1024 states cooling device ? Is the
> difference noticeable with a such small step ?

Okay, this issue is happened under MSM/Android platform. QCOM spmi wled driver
will define the max brightness. We needs to fix the issue to get thermal statistics.

Thx.

> 
> 
> > That is so large to trigger kmalloc() warning.
> > 
> > So, let's remove it and try vzalloc() if kzalloc() fails.
> > 
> > Signed-off-by: Yue Hu <huyue2@...ong.com>
> > ---
> >  drivers/thermal/thermal_sysfs.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
> > index aa99edb..9bae0b6 100644
> > --- a/drivers/thermal/thermal_sysfs.c
> > +++ b/drivers/thermal/thermal_sysfs.c
> > @@ -16,6 +16,8 @@
> >  #include <linux/device.h>
> >  #include <linux/err.h>
> >  #include <linux/slab.h>
> > +#include <linux/vmalloc.h>
> > +#include <linux/mm.h>
> >  #include <linux/string.h>
> >  #include <linux/jiffies.h>
> >  
> > @@ -919,7 +921,9 @@ static void cooling_device_stats_setup(struct thermal_cooling_device *cdev)
> >  	var += sizeof(*stats->time_in_state) * states;
> >  	var += sizeof(*stats->trans_table) * states * states;
> >  
> > -	stats = kzalloc(var, GFP_KERNEL);
> > +	stats = kzalloc(var, GFP_KERNEL | __GFP_NOWARN);
> > +	if (!stats)
> > +		stats = vzalloc(var);
> >  	if (!stats)
> >  		return;
> >  
> > @@ -938,7 +942,7 @@ static void cooling_device_stats_setup(struct thermal_cooling_device *cdev)
> >  
> >  static void cooling_device_stats_destroy(struct thermal_cooling_device *cdev)
> >  {
> > -	kfree(cdev->stats);
> > +	kvfree(cdev->stats);
> >  	cdev->stats = NULL;
> >  }
> >  
> >   
> 
>