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Bug#880203: After suspend&resume, cpufreq/scaling_max_freq is ignored

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tags 880203 - moreinfo
thanks


Ben, thank you for the clarification.

On 31.10.2017 00:35, Ben Hutchings wrote:
> Control: tag -1 moreinfo
> 
> If this system has an Intel CPU, I'm afraid this is expected behaviour.
>   They no longer allow the OS to set an exact frequency, only a 'P-
> state' (performance level).  The Linux cpufreq driver for these
> processors (intel_pstate) translates the requested frequency into a P-
> state, but the actual frequency is controlled by an embedded controller
> that may choose a higher or lower value.
> 
However, the cpufreq driver is not loaded in my case:

# lsmod | grep cpufreq
# lsmod | grep intel_pstate
#

Would loading some driver help?

Your text explains _what_ is happening, but not why the embedded 
controller chooses a higher frequency only upon suspend&resume and not 
earlier, when the root actually sets scaling_max_freq or when the 
machine is loaded with heavy applications (firefox + thunderbird + video 
player + some mathematical computation in the background + word 
processor + ...)

The way I understand it is that when the root writes to the file 
scaling_max_freq, a performance-level--setting request, let's call it R, 
goes to the embedded controller, which then chooses some frequency. 
Probably, upon suspend/resume, the controller thinks that there is more 
job to do (and, in general, there are some running applications before 
suspend which do incur work), and raises the actual frequency. Now, 
after suspend&resume, the kernel _could_, in addition to what it usually 
does, re-issue the request R to "undo" the too eager action of the 
embedded controller. If a user herself writes the same value 1200000 to 
scaling_max_freq again, nothing happens.

The current behavior might be expected from the viewpoint of the 
processor and of the embedded controller; I don't wish to question that. 
But, from the viewpoint of the user, this is extremely, overly 
_counterintuitive_. The user simply expects that the machine behaves the 
same after closing&opening the laptop lid. E.g., that if the user 
enjoyed noise-free Skype calls or noise-free music before, she expects 
noise-free Skype calls and noise-free music afterwards. The noise, in 
turn, depends on the fan, which depends on the produced heat, which 
depends on the frequency...

> Unless you can show that a different kernel version reproducibly shows
> different results, or you're not using an Intel CPU, I don't think
> there's anything to be done here.
> 
It's Intel. Unfortunately, I don't have another Linux kernel to test on 
the same machine right now.

> Ben.
> 

Here is the processor data (before suspend&resume):

$ cat /proc/cpuinfo | head -27
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 58
model name      : Intel(R) Core(TM) i7-3720QM CPU @ 2.60GHz
stepping        : 9
microcode       : 0x1c
cpu MHz         : 1200.024
cache size      : 6144 KB
physical id     : 0
siblings        : 8
core id         : 0
cpu cores       : 4
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge 
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe 
syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl 
xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor 
ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic 
popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm epb 
tpr_shadow vnmi flexpriority ept vpid fsgsbase smep erms xsaveopt dtherm 
ida arat pln pts
bugs            :
bogomips        : 5183.16
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

After s&r, the MHz value goes up to some value, up to 2600.

Best regards,
Leon

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Thread

Bug#880203: After suspend&resume, cpufreq/scaling_max_freq is ignored Leon Meier <Leon.Meier@yandex.ru> - 2017-10-30 16:00 +0100
  Processed: Re: Bug#880203: After suspend&resume, cpufreq/scaling_max_freq  is ignored owner@bugs.debian.org (Debian Bug Tracking System) - 2017-10-31 01:30 +0100
  Bug#880203: After suspend&resume, cpufreq/scaling_max_freq is ignored Ben Hutchings <ben@decadent.org.uk> - 2017-10-31 01:30 +0100
    Bug#880203: After suspend&resume, cpufreq/scaling_max_freq is ignored Leon Meier <Leon.Meier@yandex.ru> - 2017-10-31 11:20 +0100
  Bug#880203: marked as done (After suspend&resume, cpufreq/scaling_max_freq  is ignored) owner@bugs.debian.org (Debian Bug Tracking System) - 2017-10-31 11:40 +0100
  Bug#880203: closed by Ben Hutchings <ben@decadent.org.uk> (Re: Fwd: Re: Bug#880203: After suspend&resume, cpufreq/scaling_max_freq is ignored) Leon Meier <Leon.Meier@yandex.ru> - 2017-10-31 13:40 +0100
    Bug#880203: After suspend&resume, cpufreq/scaling_max_freq is ignored - (wild hack) shell script Leon Meier <Leon.Meier@yandex.ru> - 2017-11-01 13:20 +0100
      Bug#880203: After suspend&resume, cpufreq/scaling_max_freq is ignored - (wild hack) shell script Ben Hutchings <ben@decadent.org.uk> - 2017-11-01 13:50 +0100
    Bug#880203: closed by Ben Hutchings <ben@decadent.org.uk> (Re: Fwd: Re: Bug#880203: After suspend&resume, cpufreq/scaling_max_freq is ignored) Ben Hutchings <ben@decadent.org.uk> - 2017-11-01 13:50 +0100
      Bug#880203: closed by Ben Hutchings <ben@decadent.org.uk> (Re: Fwd: Re: Bug#880203: After suspend&resume, cpufreq/scaling_max_freq is ignored) Leon Meier <Leon.Meier@yandex.ru> - 2017-11-01 14:00 +0100
  Bug#880203: After suspend&resume, cpufreq/scaling_max_freq is ignored - alternative shell script Leon Meier <Leon.Meier@yandex.ru> - 2017-11-01 14:40 +0100

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