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Bug 1512991 - Kernel update broke dynamic CPU frequency
Summary: Kernel update broke dynamic CPU frequency
Status: CLOSED DUPLICATE of bug 1511701
Alias: None
Product: Fedora
Classification: Fedora
Component: kernel
Version: 26
Hardware: x86_64
OS: Linux
Target Milestone: ---
Assignee: Kernel Maintainer List
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2017-11-14 14:54 UTC by Hemant Kumar
Modified: 2017-11-14 15:39 UTC (History)
19 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Last Closed: 2017-11-14 15:39:24 UTC

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Description Hemant Kumar 2017-11-14 14:54:42 UTC
Description of problem:

I have noticed this on two different Thinkpad laptops. One running Fedora 26 (via Korora Linux actually) and another running Fedora 25. I am currently running:

Linux pern 4.13.10-100.fc25.x86_64 #1 SMP Fri Oct 27 17:05:04 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

And CPU frequency is pegged to 2700MHz always. 

Output of lscpu:

Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                8
On-line CPU(s) list:   0-7
Thread(s) per core:    2
Core(s) per socket:    4
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 94
Model name:            Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz
Stepping:              3
CPU MHz:               2700.000
CPU max MHz:           3600.0000
CPU min MHz:           800.0000
BogoMIPS:              5424.00
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              8192K
NUMA node0 CPU(s):     0-7

I looked at other stuff that can affect this and found:

~> cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver

~> cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

Something suspicious I noticed when I started powertop:

~> sudo powertop
modprobe cpufreq_stats failedLoaded 24 prior measurements
RAPL device for cpu 0
RAPL Using PowerCap Sysfs : Domain Mask f
RAPL device for cpu 0
RAPL Using PowerCap Sysfs : Domain Mask f
Devfreq not enabled

I don't know if that is related.

Comment 1 Jeremy Cline 2017-11-14 15:39:24 UTC

Thank you for the bug report. This sounds like a known issue. A fix landed in 4.13.12, but was reverted for 4.14 and is being reverted in 4.13.13 as it performs poorly on systems with many cores. A new fix is being worked on.

*** This bug has been marked as a duplicate of bug 1511701 ***

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