[Bug 197009] New: /proc/cpuinfo does not update frequency

[Bug 197009] New: /proc/cpuinfo does not update frequency

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=197009

            Bug ID: 197009
           Summary: /proc/cpuinfo does not update frequency
           Product: Power Management
           Version: 2.5
    Kernel Version: 4.13
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: cpufreq
          Assignee: linux-pm@vger.kernel.org
          Reporter: aleksey@rybalkin.org
        Regression: No

Created attachment 258537
  --> https://bugzilla.kernel.org/attachment.cgi?id=258537&action=edit
kernel config

The 4.13 kernel with intel_pstate=passive (or active) does not appear to
correctly update the CPU frequency in /proc/cpuinfo

After booting the reported frequency (but not the real frequency) is stuck on
one value and does not update:

$ grep MHz /proc/cpuinfo
cpu MHz         : 2194.859
cpu MHz         : 2194.859
cpu MHz         : 2194.859
cpu MHz         : 2194.859

hardware: ThinkPad X250
cpu: Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz
kernel: 4.13.3 vanilla (config attached)

As far as I remember this worked in 4.11 and broke after 4.12, I can double
check if needed.

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[Bug 197009] /proc/cpuinfo does not update frequency

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https://bugzilla.kernel.org/show_bug.cgi?id=197009

Doug Smythies (dsmythies@telus.net) changed:

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

--- Comment #1 from Doug Smythies (dsmythies@telus.net) ---
That is correct, and was intentional. It just lists tsc now.

To get the actual CPU frequencies, you have to use:

cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq

Or, I guess, more correctly these days:

cat /sys/devices/system/cpu/cpufreq/policy*/scaling_cur_freq

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[Bug 197009] /proc/cpuinfo does not update frequency

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https://bugzilla.kernel.org/show_bug.cgi?id=197009

Aleksey Rybalkin (aleksey@rybalkin.org) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |INVALID

--- Comment #2 from Aleksey Rybalkin (aleksey@rybalkin.org) ---
Thanks! Didn't know about that. Resolving this now.

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[Bug 197009] /proc/cpuinfo does not update frequency

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https://bugzilla.kernel.org/show_bug.cgi?id=197009

Viresh Kumar (viresh.kumar@linaro.org) changed:

           What    |Removed                     |Added
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                 CC|                            |viresh.kumar@linaro.org

--- Comment #3 from Viresh Kumar (viresh.kumar@linaro.org) ---
(In reply to Doug Smythies from comment #1)
> That is correct, and was intentional. It just lists tsc now.
> 
> To get the actual CPU frequencies, you have to use:
> 
> cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq
> 
> Or, I guess, more correctly these days:
> 
> cat /sys/devices/system/cpu/cpufreq/policy*/scaling_cur_freq

They are both pointing to the same file. The former is link to the later one.

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[Bug 197009] /proc/cpuinfo does not update frequency

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https://bugzilla.kernel.org/show_bug.cgi?id=197009

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

           What    |Removed                     |Added
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                 CC|                            |haleakalas@yahoo.com

--- Comment #4 from Zhang Rui (rui.zhang@intel.com) ---
*** Bug 197017 has been marked as a duplicate of this bug. ***

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[Bug 197009] /proc/cpuinfo does not update frequency

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https://bugzilla.kernel.org/show_bug.cgi?id=197009

Len Brown (lenb@kernel.org) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED
                 CC|                            |lenb@kernel.org
         Resolution|INVALID                     |DOCUMENTED

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[Bug 197009] /proc/cpuinfo does not update frequency

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Steven Haigh (netwiz@crc.id.au) changed:

           What    |Removed                     |Added
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                 CC|                            |netwiz@crc.id.au

--- Comment #5 from Steven Haigh (netwiz@crc.id.au) ---
I'm trying to figure out if I've hit a bug or not... My laptop CPU now doesn't
seem to clock down - meaning the temps are higher and the laptop CPU fan is
always running - even when idle.

I noticed it used the intel_pstate driver, I disabled this and tried the
acpi_cpufreq driver, however I see the following:

# cat /sys/devices/system/cpu/cpufreq/policy*/scaling_cur_freq
2828056
2890338
2889348
2800463

The frequencies supported are:
2901000 2900000 2800000 2700000 2500000 2400000 2300000 2200000 2000000 1900000
1800000 1700000 1600000 1400000 1300000 1200000

I've tried the ondemand and performance gov with no changes.

Is this an actual problem (I think so), or am I checking the freq settings in
the wrong place and the values displayed are making me bark up the wrong tree?

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[Bug 197009] /proc/cpuinfo does not update frequency

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Rob Thomas (xrobau@gmail.com) changed:

           What    |Removed                     |Added
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                 CC|                            |xrobau@gmail.com

--- Comment #6 from Rob Thomas (xrobau@gmail.com) ---
This appears to be a regression, and Linus has made it reasonably clear that
he's unhappy with regressions - 
http://lkml.iu.edu/hypermail/linux/kernel/1710.3/02474.html is a recent
example.

This breaks a bunch of userspace stuff that is relying on /proc/cpuinfo to
provide an accurate, or even SLIGHTLY accurate, representation of the current
CPU speed.

Can this be readdressed?

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[Bug 197009] /proc/cpuinfo does not update frequency

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--- Comment #7 from Rob Thomas (xrobau@gmail.com) ---
As an update, this has been fixed and backported to 4.13

https://www.spinics.net/lists/stable/msg195663.html

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[Bug 197009] /proc/cpuinfo does not update frequency

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--- Comment #8 from Hal (haleakalas@yahoo.com) ---
The "fix" in 4.13.12 was undone/reversed in 4.13.13 and subsequent releases,
including 4.13.14 and 4.14.0.
Therefore we are back to square one with this issue, whether you call it a bug,
a regression or the improvement of the code. 

This has a significant impact on power consumption on some machines, especially
laptops and passive cooling type setups.

The issue that was reported as "CPU Frequency Monitor showing the maximum
frequency of the CPU in XFCE at all times" is just the tip of the iceberg. It
is far from being a cosmetic issue. It functionally is very disruptive.

On laptops it drains the battery at a rate far greater than normal. It makes
the difference of being or not being able to use your laptop during a 4 hr
flight.

Going back to acpi_cpufreq instead of intel_pstate is a temporary solution on
some hardware, but not always, as acpi_cpufreq doesn't seem to have the same
level of power savings optimizations as in intel_pstate.

What would it take to "reopen" this issue as it looks like from a "bug" point
of view this is now set aside.

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[Bug 197009] /proc/cpuinfo does not update frequency

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--- Comment #9 from Rob Thomas (xrobau@gmail.com) ---
This ticket is specifically in regards to /proc/cpuinfo not displaying the
correct speed, which is a cosmetic issue. This has nothing to do with the
ACTUAL speed of the CPUs.

The revert of the revert was in this commit:

https://www.spinics.net/lists/stable/msg197162.html

Again, this ticket is purely about a cosmetic issue. Nothing else, as you can
see by the code.

If you're having problems with REAL power consumption, I suggest you open a new
ticket, or see if you can find an existing ticket that is your actual problem.

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[Bug 197009] /proc/cpuinfo does not update frequency

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https://bugzilla.kernel.org/show_bug.cgi?id=197009

--- Comment #10 from Hal (haleakalas@yahoo.com) ---
Hi Rob. Thanks for your message.
I opened the ticket https://bugzilla.kernel.org/show_bug.cgi?id=197017 which
was marked as a DUPLICATE of this ticket and closed. That's why I came here to
comment and ask my question.

I don't want to waste anyone's time and post in the wrong place, but in my
experience the /proc/cpuinfo has ramifications beyond just the frequency meter
showing the top speed CPU as opposed to the actual real time CPU speed, at
least in XFCE according to my experience. Here is why?

1) Starting with 4.13.0 and with every subsequent version of the kernel
(including 4.14.0), when used on Linux Mint 18.2 64bit with XFCE, it causes the
"CPU Frequency Monitor" to show the top speed of the CPU, not the actual,
instantaneous frequency (in average mode). Note that with any prior version,
that is not the case and it works as it should.

2) Now, after I posted my bug report, I was let to understand that this was
because the XFCE panel plugin read the information from the wrong location, aka
"/proc/cpuinfo" rather than
"/sys/devices/system/cpu/cpufreq/policy*/scaling_cur_freq". Then my bug report
was marked as duplicate of this one and closed.

3) Fetching the CPU info in the wrong place might be only a "cosmetic" issue if
it is not being used for anything other than just showing info on the screen.
But it seems to be used for more than that. It somehow has a direct impact on
"intel_pstate" driver which gets disturbed and results in far greater power
consumption. When I observed that, I switched to "acpi_cpufreq" driver and the
power consumption got lower but not to the minimum as it was the case with
"intel_pstate" when running with an older kernel.

I don't know where "acpi_cpufreq" is getting its CPU speed cue but somehow it
behaves better than "intel_pstate" on this affected series of kernels.

4) The only exception to this occurrence is with kernel version
4.13.12-041312-generic #201711080535, which I currently use, and which makes my
machine behave EXACTLY as it did with older kernel versions. So, for me it WAS
a solution.

5) But the fix in 4.13.12 was reversed because apparently it caused to much CPU
IPI, etc. I can understand that a different fix is necessary. But I question
the wisdom of closing this ticket, unless there is another one that I haven't
been able to find yet.

As to the "cosmetic" vs "functional" aspect of the issue, it worries me even
more because it sounds like I am the only one out there observing power
consumption issues. 

Again to reiterate, on my 6 month old Intel Pentium G4560 desktop I see this
issue, on my HP high end laptop with Intel i7-4710HQ, same behavior, and on a
low end unbranded laptop with Intel Celeron N3450 same tune! (All three systems
running Linux Mint 18.2 XFCE 64 bit in various state of update)

I understand this is not a discussion forum and only bug reports should be made
with useful information for the developers, and that's what I was trying to do.

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[Bug 197009] /proc/cpuinfo does not update frequency

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--- Comment #11 from Steven Haigh (netwiz@crc.id.au) ---
For what its worth, this seems exactly like my Comment 5 above.

I still have no solution or leads on how / where to follow this up.

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[Bug 197009] /proc/cpuinfo does not update frequency

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Rafael J. Wysocki (rjw@rjwysocki.net) changed:

           What    |Removed                     |Added
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                 CC|                            |rjw@rjwysocki.net

--- Comment #12 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
(In reply to Steven Haigh from comment #11)
> For what its worth, this seems exactly like my Comment 5 above.
> 
> I still have no solution or leads on how / where to follow this up.

Please open a separate bug entry for this.

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[Bug 197009] /proc/cpuinfo does not update frequency

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Rafael J. Wysocki (rjw@rjwysocki.net) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|DOCUMENTED                  |CODE_FIX

--- Comment #13 from Rafael J. Wysocki (rjw@rjwysocki.net) ---
Now, whatever is reported as "cpu MHz" in /proc/cpuinfo in 4.13 and later has a
little to do with the intel_pstate driver in any case.  It always comes from
some code outside of this driver, this way or another.

That said, there is mainline commit 7d5905dc14a8 (x86 / CPU: Always show
current CPU frequency in /proc/cpuinfo) causing "cpu MHz" in /proc/cpuinfo to
report the current frequency again.  It is going to be backported to 4.13.y and
4.14.y if all goes well.

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--- Comment #14 from Steven Haigh (netwiz@crc.id.au) ---
Re Comment 12 - I have lodged the issue here:
https://bugzilla.kernel.org/show_bug.cgi?id=197945

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