[Bug 209069] New: CPU stuck at 800 MHz at any load

[Bug 209069] New: CPU stuck at 800 MHz at any load

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=209069

            Bug ID: 209069
           Summary: CPU stuck at 800 MHz at any load
           Product: Power Management
           Version: 2.5
    Kernel Version: 5.8.5
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: cpufreq
          Assignee: linux-pm@vger.kernel.org
          Reporter: tg@gmplib.org
        Regression: No

Environment 1:
  OS:     GNU/Linux/Xen Gentoo 17.1 (ker=5.8.5 xen=4.12.3)
  mbd:    Supermicro X10SLH-F-O S1150 µATX (BIOS 3.3 2020-06-13)
  cpu:    Intel HWL X4 3600MHz (Xeon E3-1271v3, ECC)
  memory: 8192MB SDRAM DDR3L-1600 ECC (Samsung M391B1G73QH0-YK0Q)
  memory: 8192MB SDRAM DDR3L-1600 ECC (Samsung M391B1G73QH0-YK0Q)
  memory: 8192MB SDRAM DDR3L-1600 ECC (Samsung M391B1G73QH0-YK0Q)
  memory: 8192MB SDRAM DDR3L-1600 ECC (Samsung M391B1G73QH0-YK0Q)
  disk:   SATA SSD 2.5" 120GB Samsung SM863
  case:   Supermicro CSE-510T-203B

Environment 2. Almost identical, but with this cpu:
  cpu:    Intel BWL X4 3400MHz LLC=6M+128M (Xeon E3-1285Lv4)

I upgraded from 5.4.48 to 5.8.x for various versions of x to finally reach x =
5. Now, the systems get stuck at what is displayed as 800 MHz in /proc/cpuinfo.

When booted to run Xen, the problem goes away. When booting the (Xen
Dom0-capable) kernel without Xen, the clock gets stuck at 800 MHz at any load.

It's certainly not just a problem with /proc/cpuinfo's displayed frequency; the
systems are really, really sluggish.

A similarly configured Skylake system does NOT exhibit the same problem. (The
motherboard of that system is Supermicro X11SSM.) Similarly configured Sandy
Bridge and Westmere systems also do not exhibit this problem.

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[Bug 209069] CPU stuck at 800 MHz at any load

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https://bugzilla.kernel.org/show_bug.cgi?id=209069

Barnabás Pőcze (pobrn@protonmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pobrn@protonmail.com

--- Comment #1 from Barnabás Pőcze (pobrn@protonmail.com) ---
Can you check /sys/devices/system/cpu/cpu*/cpufreq/* and
/sys/devices/system/cpu/intel_pstate/* ?

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[Bug 209069] CPU stuck at 800 MHz at any load

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https://bugzilla.kernel.org/show_bug.cgi?id=209069

--- Comment #5 from Torbjörn Granlund (tg@gmplib.org) ---
Comment 3 was truncated by bugzilla. After the attachment, this text occurred:

hwl ~ # head /sys/devices/system/cpu/intel_pstate/*
==> /sys/devices/system/cpu/intel_pstate/max_perf_pct <==
100

==> /sys/devices/system/cpu/intel_pstate/min_perf_pct <==
20

==> /sys/devices/system/cpu/intel_pstate/no_turbo <==
0

==> /sys/devices/system/cpu/intel_pstate/num_pstates <==
33

==> /sys/devices/system/cpu/intel_pstate/status <==
passive

==> /sys/devices/system/cpu/intel_pstate/turbo_pct <==
13

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[Bug 209069] CPU stuck at 800 MHz at any load

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https://bugzilla.kernel.org/show_bug.cgi?id=209069

Doug Smythies (dsmythies@telus.net) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dsmythies@telus.net

--- Comment #6 from Doug Smythies (dsmythies@telus.net) ---
intel_cpufreq CPU frequency driver (intel_pstate in passive mode), userspace
governor with a setspeed of 0.8GHz. So, you are getting what you asked for.

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[Bug 209069] CPU stuck at 800 MHz at any load

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https://bugzilla.kernel.org/show_bug.cgi?id=209069

--- Comment #7 from Torbjörn Granlund (tg@gmplib.org) ---
bugzilla-daemon@bugzilla.kernel.org writes:

  intel_cpufreq CPU frequency driver (intel_pstate in passive mode), userspace
  governor with a setspeed of 0.8GHz. So, you are getting what you asked for.

I will gladly confess my ignorance about this.

But...I've maintained these systems for a long time, and gradually upgraded
the kernels (as well as the user space).  The CPU_FREQ_GOV_USERSPACE
setting was inherited from some old default, and indeed is used by many
older kernels.

Only 5.8.x suddenly make Haswell and Broadwell run at 800 MHz.  Skylake is
not affected by this at all.  With 5.4.x, the systems run at their nominal
frequencies.

If this is a desired change in kernel behaviour, then many people might
see their systems slow down radically.

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[Bug 209069] CPU stuck at 800 MHz at any load

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https://bugzilla.kernel.org/show_bug.cgi?id=209069

--- Comment #8 from Doug Smythies (dsmythies@telus.net) ---
My best guess is that with kernel 5.4.48 you were running with the intel_pstate
CPU frequency scaling driver in active mode, and that you are now running in
passive mode. As of kernel 5.8-rc1 by default processors without HWP will
default to passive mode. If you still have kernel 5.4.48, you could check.

Your Skylake system has HWP, and wouldn't default to passive mode.

However, you also mentioned Sandy Bridge and Westmere systems being unaffected.
Sandy Bridge doesn't have HWP, and Westmere might even pre-date the pstate
driver, I don't know. Anyway, this seems inconsistent with my "best guess"
above. Suggest you check them, with those same instructions from comment 1.

If you think, or conclude, that you used to run in active mode you can either
force active mode or force the schedutil governor in passive mode via the grub
command line to get out of your locked low frequency state.

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[Bug 209069] CPU stuck at 800 MHz at any load

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https://bugzilla.kernel.org/show_bug.cgi?id=209069

Oleh Vinichenko (moonlapse81@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |moonlapse81@gmail.com

--- Comment #9 from Oleh Vinichenko (moonlapse81@gmail.com) ---
I hit this issue as well. On Lenovo ThinkPad W520, with SandyBridge CPU,
Intel(R) Core(TM) i7-2860QM. gradually updated through versions 5.8.* from
older kernels, while keeping kernel configuration the same. If this new change
to be expected as default, there must be documentation about this new behaviour
and what is required to keep active state. What is required to change in kernel
configuration, if needed. This caused massive compilation time regressions and
shoudl not be cast on users without update steps.

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[Bug 209069] CPU stuck at 800 MHz at any load

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https://bugzilla.kernel.org/show_bug.cgi?id=209069

--- Comment #11 from Doug Smythies (dsmythies@telus.net) ---
Created attachment 292363
  --> https://bugzilla.kernel.org/attachment.cgi?id=292363&action=edit
example of needed information

Please, we need more information. Do you know for certain that you were
defaulting to "active" mode before and now "passive" mode. What is your kernel
configuration in the CPU frequency scaling area? What, if anything, is
specified on your grub command line? What governor to you end up with?

attached is an example of needed information.

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[Bug 209069] CPU stuck at 800 MHz at any load

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https://bugzilla.kernel.org/show_bug.cgi?id=209069

--- Comment #14 from Doug Smythies (dsmythies@telus.net) ---
Thanks. I re-created your results on my no-hwp processor, by also setting this
in my kernel configuration:

< CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y
< # CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE is not set
---
> # CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE is not set
> CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE=y

The related commits are:

a00ec3874e7d cpufreq: intel_pstate: Select schedutil as the default governor
33aa46f252c7 cpufreq: intel_pstate: Use passive mode by default without HWP

I had thought it would default to the schedutil governor, but didn't.

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[Bug 209069] CPU stuck at 800 MHz at any load

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https://bugzilla.kernel.org/show_bug.cgi?id=209069

--- Comment #16 from Doug Smythies (dsmythies@telus.net) ---
Hi Rui,

Actually, e-mails about this bug report are on list, because it hasn't been
assigned.

I my opinion, this one can be closed because

CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE=y

doesn't have a consistent meaning.
(And I argued this very point with Dirk Brandewie, the original author and
maintainer of the intel_pstate CPU frequency scaling driver, around 2013)

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[Bug 209069] CPU stuck at 800 MHz at any load - Xeon E3-1271v3 HSW

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https://bugzilla.kernel.org/show_bug.cgi?id=209069

Zhang Rui (rui.zhang@intel.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |WILL_NOT_FIX
            Summary|CPU stuck at 800 MHz at any |CPU stuck at 800 MHz at any
                   |load                        |load - Xeon E3-1271v3 HSW

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[Bug 209069] CPU stuck at 800 MHz at any load - Xeon E3-1271v3 HSW

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Zhang Rui (rui.zhang@intel.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

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