RE: [PATCH 09/10] tools/power turbostat: Print cpuidle information

["Doug Smythies" <dsmythies@telus.net>]

Hi Len, Antti,

I didn't actually try it yet.
This reply is just from reading the patches.

On 2020.03.19 22:23 Len Brown wrote:

> From: Antti Laakso <antti.laakso@linux.intel.com>
>
> Print cpuidle driver and governor.
>
> Signed-off-by: Antti Laakso <antti.laakso@linux.intel.com>
> Signed-off-by: Len Brown <len.brown@intel.com>

...

> +	sprintf(path, "/sys/devices/system/cpu/cpuidle/current_governor_ro");
> +	input = fopen(path, "r");
> +	if (input == NULL) {
> +		fprintf(outf, "NSFOD %s\n", path);
> +		return;
> +	}
> +	if (!fgets(cpuidle_buf, sizeof(cpuidle_buf), input))
> +		err(1, "%s: failed to read file", path);
> +	fclose(input);
> +
> +	fprintf(outf, "cpuidle governor: %s", cpuidle_buf);
> +

There is a problem here if one has the 'cpuidle_sysfs_switch'
in the kernel command line (which I do always), because that
(not) variable name changes as a function of the switch [2].

I have:

$ grep . /sys/devices/system/cpu/cpuidle/*
/sys/devices/system/cpu/cpuidle/available_governors:ladder menu teo
/sys/devices/system/cpu/cpuidle/current_driver:intel_idle
/sys/devices/system/cpu/cpuidle/current_governor:teo

And in grub:

GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 consoleblank=300 intel_pstate=passive cpuidle_sysfs_switch cpuidle.governor=teo"

Note that there was talk of getting rid of the command line switch [1 at the end], which would be great.
Copied below:

On 2019.09.02 14:59 Rafael wrote:

> FWIW, I've been thinking about getting rid of the cpuidle_sysfs_switch
> command line option and always allowing user space to switch cpuidle
> governors at run time.  At least I see no reason why that would not
> work ATM.

[1] https://marc.info/?l=linux-pm&m=156746153919195&w=2
[2] Documentation/admin-guide/pm/cpuidle.rst (search for 'current_governor_ro')

... Doug