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4.13.12 kernel causes cpu freq to lock to max, system hot
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RayDude
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PostPosted: Sat Nov 11, 2017 6:50 pm    Post subject: 4.13.12 kernel causes cpu freq to lock to max, system hot Reply with quote

I upgraded to 4.13.12 kernel and the Ryzen is stuck at 3700 MHz. It worked fine with 4.12, any idea what changed?

Here's the kernel config. I copied it from the previous kernel and then added features trying to get it to work...

Code:

-*- CPU Frequency scaling                                                                                  │ │ 
  │ │                                     [*]   CPU frequency transition statistics                                                                  │ │ 
  │ │                                           Default CPUFreq governor (ondemand)  --->                                                            │ │ 
  │ │                                     -*-   'performance' governor                                                                               │ │ 
  │ │                                     <*>   'powersave' governor                                                                                 │ │ 
  │ │                                     <*>   'userspace' governor for userspace frequency scaling                                                 │ │ 
  │ │                                     -*-   'ondemand' cpufreq policy governor                                                                   │ │ 
  │ │                                     <*>   'conservative' cpufreq governor                                                                      │ │ 
  │ │                                     [*]   'schedutil' cpufreq policy governor                                                                  │ │ 
  │ │                                           *** CPU frequency scaling drivers ***                                                                │ │ 
  │ │                                     -*-   Intel P state control                                                                                │ │ 
  │ │                                     <*>   Processor Clocking Control interface driver                                                          │ │ 
  │ │                                     <M>   ACPI Processor P-States driver                                                                       │ │ 
  │ │                                     [*]     Legacy cpb sysfs knob support for AMD CPUs                                                         │ │ 
  │ │                                     <M>   AMD Opteron/Athlon64 PowerNow!                                                                       │ │ 
  │ │                                     <M>   AMD frequency sensitivity feedback powersave bias                                                    │ │ 
  │ │                                     < >   Intel Enhanced SpeedStep (deprecated)                                                                │ │ 
  │ │                                     < >   Intel Pentium 4 clock modulation                                                                     │ │ 
  │ │                                           *** shared options ***


acpu_cpufreq is loaded:

Code:

lsmod | grep acpi           
acpi_cpufreq           20480  0


The behavior of /proc/cpuinfo may have changed. It used to report actual frequency. Now it seems to report max frequency.

Code:

cat /proc/cpuinfo | grep MHz
cpu MHz         : 3692.860
cpu MHz         : 3692.860
cpu MHz         : 3692.860
cpu MHz         : 3692.860
cpu MHz         : 3692.860
cpu MHz         : 3692.860
cpu MHz         : 3692.860
cpu MHz         : 3692.860
cpu MHz         : 3692.860
cpu MHz         : 3692.860
cpu MHz         : 3692.860
cpu MHz         : 3692.860


But cpufreq is trying to run the cores at 1550:

Code:

cat /sys/devices/system/cpu/cpu?/cpufreq/cpuinfo_cur_freq
1550000
1550000
1550000
1550000
1550000
1550000
1550000
1550000
1550000
1550000


Has anyone seen or dealt with this? What is actually going on?

The only reason I doubt the numbers from cpufreq is the fact that the case is much warmer with this kernel than it was with the last.
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tholin
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PostPosted: Sat Nov 11, 2017 8:09 pm    Post subject: Re: 4.13.12 kernel causes cpu freq to lock to max, system ho Reply with quote

RayDude wrote:
The behavior of /proc/cpuinfo may have changed. It used to report actual frequency. Now it seems to report max frequency.

Yes, it was changed in v4.13-rc1 with this patch:
https://github.com/torvalds/linux/commit/51204e0639c49ada02fd823782ad673b6326d748
However some people relied on the info in /proc/cpuinfo so this was a userspace breaking change and Linus wasn't happy.
https://bugzilla.kernel.org/show_bug.cgi?id=197009
The patch was reverted in v4.14-rc8:
https://github.com/torvalds/linux/commit/890da9cf098364b11a7f7f5c22fa652531624d03
Turns out it wasn't as easy as just reverting it and other patches has been added ontop to fix problems. Last one was added yesterday.

But your heat problem is probably not related to the /proc/cpuinfo change.
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RayDude
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PostPosted: Sun Nov 12, 2017 7:20 pm    Post subject: Re: 4.13.12 kernel causes cpu freq to lock to max, system ho Reply with quote

tholin wrote:
RayDude wrote:
The behavior of /proc/cpuinfo may have changed. It used to report actual frequency. Now it seems to report max frequency.

Yes, it was changed in v4.13-rc1 with this patch:
https://github.com/torvalds/linux/commit/51204e0639c49ada02fd823782ad673b6326d748
However some people relied on the info in /proc/cpuinfo so this was a userspace breaking change and Linus wasn't happy.
https://bugzilla.kernel.org/show_bug.cgi?id=197009
The patch was reverted in v4.14-rc8:
https://github.com/torvalds/linux/commit/890da9cf098364b11a7f7f5c22fa652531624d03
Turns out it wasn't as easy as just reverting it and other patches has been added ontop to fix problems. Last one was added yesterday.

But your heat problem is probably not related to the /proc/cpuinfo change.


I had seen the thread with Linus flaming a developer. I hadn't realized it was this change.

The heat may just be the fans being controlled better. Although I thought that was controlled by the BIOS and it's definitely a difference between the kernels.

I'll look for the stable 4.14 when it comes out.

Thanks.
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