Public bug reported:
A few days ago, when Vivid was still at Linux 3.18 I tried the Linux
4.0-rc1 kernel from mainline and noticed that CPU frequency scaling
would have no effect on the actual processor speed. I went back to 3.18
and everything worked fine.
Now Ubuntu 15.04 moved to Linux 3.19 and it happens to have the same
problem as with 4.0-rc1 from mainline.
The cpufreq indicator shows that the frequencies are adapted but
> watch sudo cpupower monitor
reveals that the AMD A10 PRO-7350B CPUs are stuck at the lowest frequency level
(about 1.1GHz).
This observation is confirmed by a quick benchmark using octave.
The following line is executed on Linux 3.18 in less than 4 seconds, while on
Linux 3.19 it needs more than 8 seconds to complete.
> time echo "a=rand(3000);a*a;" | octave -q
ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: linux-image-3.19.0-7-generic 3.19.0-7.7
ProcVersionSignature: Ubuntu 3.19.0-7.7-generic 3.19.0
Uname: Linux 3.19.0-7-generic x86_64
ApportVersion: 2.16.2-0ubuntu1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: marc 2515 F.... pulseaudio
/dev/snd/controlC0: marc 2515 F.... pulseaudio
CurrentDesktop: Unity
Date: Mon Mar 2 19:04:32 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-02-23 (7 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Alpha amd64 (20150219)
MachineType: Hewlett-Packard HP EliteBook 755 G2
ProcFB: 0 radeondrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.19.0-7-generic
root=UUID=1a54cd72-80fc-4716-a62e-4faa5dcc63e9 ro quiet splash vt.handoff=7
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/19/2014
dmi.bios.vendor: Hewlett-Packard
dmi.bios.version: M84 Ver. 01.01
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: 221C
dmi.board.vendor: Hewlett-Packard
dmi.board.version: KBC Version 63.13
dmi.chassis.asset.tag: CNU426C7YS
dmi.chassis.type: 10
dmi.chassis.vendor: Hewlett-Packard
dmi.modalias:
dmi:bvnHewlett-Packard:bvrM84Ver.01.01:bd05/19/2014:svnHewlett-Packard:pnHPEliteBook755G2:pvrA3009DD10303:rvnHewlett-Packard:rn221C:rvrKBCVersion63.13:cvnHewlett-Packard:ct10:cvr:
dmi.product.name: HP EliteBook 755 G2
dmi.product.version: A3009DD10303
dmi.sys.vendor: Hewlett-Packard
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug vivid
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https://bugs.launchpad.net/bugs/1427330
Title:
AMD Kaveri APU/CPU frequency scaling not working on linux 3.19
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