Re: [PATCH v1] thermal/core: change mm alloc method to avoid kernel warning

[Daniel Lezcano]

On 19/04/2022 15:54, Zhang Rui wrote:
> CC Viresh.
>
> On Tue, 2022-04-19 at 11:14 +0200, Daniel Lezcano wrote:
> > On 19/04/2022 10:48, Zhang Rui wrote:
> > > On Sun, 2022-04-17 at 12:56 +0000, Junwen Wu wrote:
> > > > Very high cooling device max state value makes cooling device
> > > > stats
> > > > buffer allocation fails,like below.Using kzvalloc instead of
> > > > kzalloc
> > > > can avoid this issue.
> > >
> > > When a cooling device has big max_state, this patch can get ride of
> > > the
> > > warning here, but still we end up with the read failure of the
> > > trans_table in sysfs because it is larger than PAGE_SIZE.
> > >
> > > $ cat /sys/class/thermal/cooling_device8/stats/trans_table
> > > cat: /sys/class/thermal/cooling_device8/stats/trans_table: File too
> > > large
> > >
> > > IMO, unless we can fix both places, I'd suggest we skip allocating
> > > and
> > > creating the broken trans_table attr. Like a prototype patch below
> >
> > Why not create a thermal debugfs with real useful information and
> > get
> > rid of this broken code ?
>
> The idea looks good to me.

What about doing a percentile approach of the state indexes changes 
instead of a raw matrix full of zeros ? So we show the most significant 
transitions, perhaps something like:

99%:	7->6	6->7
98%:	6->5	5->6
95%:	5->4	4->5
90%:	7->5	5->7
80%:	6->4	4->6
70%:	7->1	7->2
50%:	...	...

total:	123456	124573


And another statistics file containing some timings information like the 
total duration in mitigation, and the duration in the most significant 
states above?

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