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Bug 451845 - Unable to throttle a Pentium 4 CPU.
Summary: Unable to throttle a Pentium 4 CPU.
Alias: None
Product: Fedora
Classification: Fedora
Component: kernel
Version: 9
Hardware: i386
OS: Linux
Target Milestone: ---
Assignee: John Feeney
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2008-06-17 19:07 UTC by Joonas Sarajärvi
Modified: 2013-01-10 07:04 UTC (History)
3 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2008-11-26 20:18:19 UTC

Attachments (Terms of Use)
Output of /sbin/lspci (deleted)
2008-06-17 19:07 UTC, Joonas Sarajärvi
no flags Details
Output of /sbin/lsmod (deleted)
2008-06-17 19:08 UTC, Joonas Sarajärvi
no flags Details
Output of cat /proc/cpuinfo (deleted)
2008-06-17 19:11 UTC, Joonas Sarajärvi
no flags Details
Output of cat /proc/acpi/processor/CPU0/info (deleted)
2008-06-17 19:13 UTC, Joonas Sarajärvi
no flags Details
Output of modprobe acpi_cpufreq (deleted)
2008-06-17 19:16 UTC, Joonas Sarajärvi
no flags Details

Description Joonas Sarajärvi 2008-06-17 19:07:34 UTC
Description of problem:
CPU always runs on full power, regardless of load. Selecting a power management
scheme from KPowersave does not affect anything.

Version-Release number of selected component (if applicable):

How reproducible:
Always, on this specific hardware.

Steps to Reproduce:
1. Install Fedora 9 from the KDE live media.
2. Click the KPowersave icon in the tray.
Actual results:
CPU is at 100% power.

Expected results:
Should see the CPU on a low power state instead of the full power state.

Additional info:
Output of lspci, lsmod and a few other commands added as attachments.

Comment 1 Joonas Sarajärvi 2008-06-17 19:07:34 UTC
Created attachment 309658 [details]
Output of /sbin/lspci

Comment 2 Joonas Sarajärvi 2008-06-17 19:08:34 UTC
Created attachment 309659 [details]
Output of /sbin/lsmod

Comment 3 Joonas Sarajärvi 2008-06-17 19:11:28 UTC
Created attachment 309660 [details]
Output of cat /proc/cpuinfo

Comment 4 Joonas Sarajärvi 2008-06-17 19:13:12 UTC
Created attachment 309661 [details]
Output of cat /proc/acpi/processor/CPU0/info

Comment 5 Joonas Sarajärvi 2008-06-17 19:16:26 UTC
Created attachment 309663 [details]
Output of modprobe acpi_cpufreq

Comment 6 Dave Jones 2008-06-17 19:17:59 UTC
I'm assuming by 'throttling' you mean 'run at different speeds'.  Your CPU
doesn't actually support this feature.  In earlier releases, you were using
'p4-clockmod', which faked the appearance of running at different speeds, by
inserting 'pauses' between running instructions.  This doesn't actually save any
power (which is why it got removed).

Matthew has been working on making ACPI 'do the right thing' in the absence of
working throttling states.  Faking P-states is completely the wrong thing to do
however, so kpowersave/cpuspeed/cpufreq-applet will never work on your hardware.

Looking at your acpi/processor/info output though, it looks like your cpu/bios
doesn't expose T-states either.

Comment 7 Joonas Sarajärvi 2008-06-17 19:22:13 UTC
Thank you for the fast response. It seems I was then just misinformed about the
actual functionality.

Comment 8 Joachim Frieben 2008-09-02 12:01:18 UTC
I have noticed that after loading p4-clockmod.ko on an Intel Celeron 2 GHz desktop system running kernel 2.6.18-92.1.10.el5, minimum and maximum frequencies are both set to 20000000. Thus, there is no scaling at all whereas the clock is adjusted dynamically for kernel which has been added for testing purposes. Is this change an intended one follwing the reasoning of comment #6?

Comment 9 Joachim Frieben 2008-09-02 12:09:44 UTC
(In reply to comment #8)

more /proc/acpi/processor/CPU1/info 
processor id:            0
acpi id:                 1
bus mastering control:   no
power management:        no
throttling control:      yes
limit interface:         yes

more /proc/acpi/processor/CPU1/throttling 
state count:             8
active state:            T0
   *T0:                  00%
    T1:                  12%
    T2:                  25%
    T3:                  37%
    T4:                  50%
    T5:                  62%
    T6:                  75%
    T7:                  87%

Comment 10 Joachim Frieben 2008-11-26 07:51:33 UTC
(In reply to comment #9)
After installing F10 plus updates including kernel-, the p4-clockmod module is present and can be loaded. However, the cpuspeed daemon cannot be started, and /sys/devices/system/cpu/cpu0/cpufreq/ is empty.
However, dmesg actually reports:

  "p4-clockmod: P4/Xeon(TM) CPU On-Demand Clock Modulation available"

upon loading of module p4-clockmod.

Comment 11 Dave Jones 2008-11-26 20:18:19 UTC
this is expected behaviour.  The user-interface is meant to be disabled.  The ACPI code will call into the p4-clockmod code directly when throttling is necessary.

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