linux-kernel - Re: [PATCH v4] cpufreq: stats: Add 'load_table' debugfs file to show accumulated data of CPUs

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Date:	Tue, 02 Jul 2013 19:49:30 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	rjw@...k.pl, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, cpufreq@...r.kernel.org,
	kyungmin.park@...sung.com, myungjoo.ham@...sung.com
Subject: Re: [PATCH v4] cpufreq: stats: Add 'load_table' debugfs file to show
 accumulated data of CPUs

Hi Viresh,

Previously, I sent two reply about your reply. But, Please ignore previous reply.
Those have wrong function flow about creating sysfs file and poor wrong opinion.

I'm so sorry if you're confused.

On 06/28/2013 07:13 PM, Viresh Kumar wrote:
> On 28 June 2013 14:52, Chanwoo Choi <cw00.choi@...sung.com> wrote:
>> On 06/28/2013 05:18 PM, Viresh Kumar wrote:
>>> On 28 June 2013 13:18, Chanwoo Choi <cw00.choi@...sung.com> wrote:
> 
>>> Can you describe a bit about the layout this will create in debugfs?
>>> I thought you will have a load_table file per policy->cpu ??
>>>
>>
>> The debugfs_cpufreq is debugfs root directory (/sys/kernel/debug/cpufreq)
> 
> Which you are creating anyway in your patch.
> 
>> and debugfs_cpufreq has many child directory for Per-CPU debugfs according to NR_CPUS number (/sys/kernel/debug/cpufreq/cpuX).
> 
> Even you are creating this only for policy->cpu
> 
>> Finally, Per-CPU debugfs create load_table debugfs file (/sys/kernel/debug/cpufreq/cpuX/load_table).
>>
>> For example, only CPU0 create sysfs directory and file (/sys/devices/system/cpu/cpu0/cpufreq)
>> and then other CPUx create link of created sysfs directory by CPU0 in cpufreq_add_dev_symlink().
> 
> This isn't how its happening now. You aren't creating any links.

You're right. This patch didn't create link for CPU1/2/3.

> 
>> So, I'm considering whether to create link of CPUx's debugfs file except for CPU0 as sysfs file.
>> - /sys/kernel/debug/cpufreq/cpu1/
>> - /sys/kernel/debug/cpufreq/cpu2/
>> - /sys/kernel/debug/cpufreq/cpu3/
> 
> Yes please.

OK. I'll create link for CPU[1-3] if multiple core use one cpufreq policy.
In result, we can check below directory structure.

sh-4.1# ls -al /sys/kernel/debug/cpufreq/
total 0
drwxr-xr-x  3 root root 0 Jan  1 09:00 .
drwx------ 26 root root 0 Jan  1 09:00 ..
drwxr-xr-x  2 root root 0 Jan  1 09:00 cpu0
lrwxrwxrwx  1 root root 0 Jan  1 09:00 cpu1 -> ./cpu0
lrwxrwxrwx  1 root root 0 Jan  1 09:00 cpu2 -> ./cpu0
lrwxrwxrwx  1 root root 0 Jan  1 09:00 cpu3 -> ./cpu0

And then I will create load_table debugfs file below of /sys/kernel/debug/cpufreq/cpu0
in cpufreq_stats.c

> 
>> - A number of online CPU is 4
>> Time(ms)   Old Freq(Hz) New Freq(Hz) CPU0 CPU1 CPU2 CPU3
>> 23165      200000       200000       2    0    0    0
>> 23370      200000       200000       2    0    0    0
>> 23575      200000       200000       2    0    1    0
>> 23640      200000       200000       5    1    1    0
>> 23780      200000       200000       3    0    1    0
>> 23830      200000       200000       7    1    0    0
>> 23985      200000       200000       1    0    0    0
>> 24190      200000       200000       2    0    1    1
>> 24385      200000       200000       2    0    0    0
>> 24485      200000       200000       6    0    1    0
>>
>> - A number of online CPU is 2
>> Time(ms)   Old Freq(Hz) New Freq(Hz) CPU0 CPU3
>> 37615      200000       200000       0    0
>> 37792      200000       200000       0    5
>> 38015      200000       200000       21   8
>> 38215      200000       200000       0    0
>> 38275      200000       200000       5    0
>> 38415      200000       200000       15   3
>> 38615      200000       200000       0    0
>> 38730      200000       200000       1    0
>> 38945      200000       200000       0    0
>> 39155      200000       200000       1    1
> 
> If you do the loop over for_each_cpu(cpu, policy->cpus),
> this problem will be resolved. You will see only online cpus.
> 
>> I'm considering whether to check the kind of cpufreq governor for creating load_table
>> in cpufreq_stats or execute dbs_check_cpu() on performance/powersave governor to check
>> CPUx load. If you have opinion about this, I'd like to listen it.
> 
> Maybe create these directories and do this stuff only when
> the first CPUFREQ_LOADCHECK notification is received inside
> cpufreq_stats.c
> 
> Also don't create debug/cpufreq directory unless you have any
> stuff to be created within this directory. Like, don't create it
> if we are using performance governor for all cpus.

I understand your opinion. But I have a suggestion for using load_table debugfs file
if cpufreq governor is performance/powersave.

So, I suggest that performance/powersave governor may need to executes dbs_check_cpu()
to calculate CPUx load. Sometimes, we need CPUs load on performance/powersave
govenor because we could get different power-consumption according to CPUs load
on same cpu frequency when we estimate power-consumption on specific test case.

I think we need to check CPUs load on peformance/powersave governor.

What is your opinion?

Best Regards,
Chanwoo Choi


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