Public bug reported:
I have noticed slow performance after resuming from STR on battery.
I can not trigger this always, but it seems to be related to suspending
and resuming while on battery.
The CPU scaling governors look like this then:
% cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
powersave
performance
performance
performance
% cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_driver
intel_pstate
intel_pstate
intel_pstate
intel_pstate
% cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq
3200000
3200000
3200000
3200000
When watching the current CPU frequencies, it can be seen that they
don't go above 800000 ('watch grep \"cpu MHz\" /proc/cpuinfo').
I cannot see why they are limited to 800000.
It looks like https://bugzilla.kernel.org/show_bug.cgi?id=61241, but
/sys/devices/system/cpu/intel_pstate/max_perf_pct is at 100.
Just writing the same setting for cpu0 again fixes it, and all CPUs will
be scaled above 800MHz again:
% echo powersave | sudo tee
/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: linux-image-3.19.0-28-generic 3.19.0-28.30
ProcVersionSignature: Ubuntu 3.19.0-28.30-generic 3.19.8-ckt5
Uname: Linux 3.19.0-28-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.4
Architecture: amd64
CurrentDesktop: Unity
Date: Sat Sep 19 10:39:02 2015
HibernationDevice: RESUME=UUID=d39463f5-889e-42ba-a729-f3f442f0c8dd
InstallationDate: Installed on 2012-05-28 (1208 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64
(20120425)
MachineType: LENOVO 42992PG
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.19.0-28-generic
root=/dev/mapper/vg0-rootlv ro quiet splash
RelatedPackageVersions:
linux-restricted-modules-3.19.0-28-generic N/A
linux-backports-modules-3.19.0-28-generic N/A
linux-firmware 1.143.3
SourcePackage: linux
UpgradeStatus: Upgraded to vivid on 2015-05-14 (127 days ago)
dmi.bios.date: 05/14/2015
dmi.bios.vendor: LENOVO
dmi.bios.version: 8DET70WW (1.40 )
dmi.board.asset.tag: Not Available
dmi.board.name: 42992PG
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias:
dmi:bvnLENOVO:bvr8DET70WW(1.40):bd05/14/2015:svnLENOVO:pn42992PG:pvrThinkPadX220Tablet:rvnLENOVO:rn42992PG:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 42992PG
dmi.product.version: ThinkPad X220 Tablet
dmi.sys.vendor: LENOVO
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Confirmed
** Tags: amd64 apport-bug third-party-packages vivid
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https://bugs.launchpad.net/bugs/1497520
Title:
Slow performance after resuming from/on battery (CPUs do not scale
above 800MHz)
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