linux-kernel - Re: [PATCH] cpufreq: stats: Do not populate stats when policy->cur has no exact match

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Date:	Mon, 18 Nov 2013 09:08:09 -0600
From:	Nishanth Menon <nm@...com>
To:	viresh kumar <viresh.kumar@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	<cpufreq@...r.kernel.org>, <linux-pm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <ceh@...com>,
	Tobias Diedrich <ranma+xen@...edrich.de>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH] cpufreq: stats: Do not populate stats when policy->cur
 has no exact match

On 11/15/2013 11:22 PM, viresh kumar wrote:
> On Saturday 16 November 2013 06:40 AM, Rafael J. Wysocki wrote:
>> On Friday, November 15, 2013 06:20:43 PM Nishanth Menon wrote:
> 
>>> So, instead of having a statistics information that never ever
>>> reflects valid data in the mentioned case and scratching our heads, we
>>> instead, refuse to populate any of the statistics entries and note in
>>> kernel log the error condition for developers to fix. The only useable
> 
> s/useable/usable
> 
>>> information are the available frequencies which is already available
>>> in other cpufreq sysfs entries.
> 
>> I like this one.  Any objections from anyone?
> 
> Well nothing against the patch but I have other thoughts. There are platforms
> which might have no choice of fixing this issue as their bootloaders might be
> setting boot freq to any value outside of our freq table.
> 
> And those might not have a chance to fix that in driver as well in case they are
> using something like cpufreq-cpu0..
> 
> So, eventually this patch wouldn't do anything except giving a boot time error
> and not initializing any stats at all..
> 
> Wouldn't it be better to create another frequency in all these tables, which
> will be an *Invalid* frequency.. With a value of -1 (i.e. largest value of an
> unsigned int) ??
> 
> And so nobody will ever miss stats again, even if they are running on invalid
> frequencies. We will capture that information too:
> - we have moved from/to invalid frequency to/from a valid/invalid frequency this
> much times.
> - We have stayed at valid/invalid frequencies for this much time.
> 
> I have a untested patch for this. If this looks okay, Nishant can you please try
> below patch? With some fixups from your side :)

http://pastebin.mozilla.org/3628975

I agree that it does show something, but would we not rather prefer to
stick with the entries available in freq_table than have to deal with
invalid frequencies that may be provided by the driver? for example:
how do we in stat know that there will only be one invalid frequency
request?


> 

[..]
> (@Rafael: Finally I have moved to thunderbird, found a way out, so no more
> crappy attachments from me :))
> 
there are some patch wrapping that thunderbird tends to do - I prefer
mutt that way, when I need to send inline patches :).

-- 
Regards,
Nishanth Menon
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