Bug 1045844

Summary:	After Kernel Upgrade to 3.12 cpu always run max frequency
Product:	[Fedora] Fedora	Reporter:	Mario Kothe <mario.kothe>
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	high	Docs Contact:
Priority:	unspecified
Version:	20	CC:	bjoern, ercantopalak, gansalmon, itamar, jonathan, kernel-maint, madhu.chinakonda
Target Milestone:	---
Target Release:	---
Hardware:	x86_64
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2014-01-06 15:18:18 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:

Description Mario Kothe 2013-12-22 13:30:18 UTC

Description of problem:

Freshly installed Fedora 20 to a new Desktop system. (Desktop KDE). After Installation the newest Update were installed. Including the Upgrade from Kernel 3.11 to 3.12. After the Upgrade (reboot) into new kernel (3.12) the System Power Management is not scaling the frequency of the cpu. The CPU is always stays at max. MHz. In my case 3.1GHz.

System is an Intel i7-4770s on an ASUS H87M-Pro

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

Ferdora 20 with Kernel 3.12

How reproducible:

Just boot with the kernel 3.12 and the CPU stays it max CPU Power. Booting with 3.11 solves the problem. The frequency of the CPU is throtteled to 800 MHz as it should

Steps to Reproduce:
1. Boot the Kernel 3.12 instead of Kernel 3.11
2.
3.

Actual results:

System stays at max CPU MHz

Expected results:

Throtteling the cpu frequency if the system is not busy.

Additional info:

Found a thread in which was mentioned that there is a new kernel component for intel cpus. intel_pstate which might be the cause of the problem. 

https://bbs.archlinux.org/viewtopic.php?pid=1294415#p1294415

The Fedora Documentation mentions the tool cpupower. That tool is not present on Fedora 20 and on an older installation Fedora 17.

Comment 1 Björn Ruberg 2014-01-05 12:27:06 UTC

This is probably not a bug. Modern CPUs save more power when they stay at the highest clock rate. They save power by switching into C-States which do conserve power very well. The higher the clock rate, the longer they can stay in that powersaving mode.

According to the source you quoted the new intel pstate driver does exactly it while knowing which CPUs are better in power saving on the high clock rate and which not. At least I read that out of it.

You have one of the latest intel processors - perfect candidate for saving power without reducing clock rates.

Comment 2 Josh Boyer 2014-01-06 15:18:18 UTC

The situation is as Björn describes it as far as I know.

Comment 3 Mario Kothe 2014-01-06 16:53:41 UTC

May be I was not clear enough. Kernel 3.11 of Fedora scales correctly. 3.12 is not doing anything of the sort. I would say that it is a bug expect you say it is correct that the CPU stay at maximum frequenticy even when the system has nothing to do. Idle at 90% for hours.

Nevermind. Deinstalled Fedora and changed to Linux Mint. After using Fedora since Fedora 8.

Comment 4 Ercan Topalak 2014-01-25 20:40:15 UTC

I've had the same problem, if you are hating fan noise, convert intel_pstate to old acpi driver with "intel_pstate=disable" kernel paramater on startup.