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[Bug 1567316] [NEW] CPU maximum frequency goes down after every resume


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This bug applies to Ubuntu 15.10, kernel 4.2.0-35-generic and at least
two before that.

A while ago I noticed that my system had become unbearably slow. A reboot fixed it for a while.
It turns out that the problem is related to resuming after closing the laptop lid. After every resume the CPU maximum frequency goes down a bit.

This was not always the case and seems to have been introduced after a
kernel update. Sadly, I can't pinpoint which one exactly.

It can be reproduced on my Lenovo B50-70 even after the latest kernel
update to 4.2.0-35-generic of Ubuntu 15.10.

I start by rebooting the system.
At first, 'sudo cpupower frequency-info' reports a hardware limit of 800 MHz - 2.60 GHz and current policy is between those two.
Current frequency varies between those based on load.
Now, I close the lid, reopen and check again.
Hardware limits are still the same, but policy is now between 800 MHz and 2.08 GHz.
Repeat and policies maximum keeps dropping. As does the current frequency maximum.
At some point the policy maximum does not drop any further, but the current frequency maximum does. Way below even the minimum of 800 MHz.

The expected behaviour is that the current policy matches the hardware
limits and that the CPU frequency is set between these values.

Here is the output of 'sudo cpupower frequency-info' after the first

analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 0.97 ms.
  hardware limits: 800 MHz - 2.60 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 800 MHz and 2.08 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 1.03 GHz (asserted by call to hardware).
  boost state support:
    Supported: yes
    Active: yes

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

** Tags: bot-comment
CPU maximum frequency goes down after every resume
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