Bug 591448 - Performance degradation with AMD PhenomII X6 Turbo-Core feature
Performance degradation with AMD PhenomII X6 Turbo-Core feature
Status: CLOSED ERRATA
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
13
x86_64 Linux
low Severity medium
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Assigned To: Kernel Maintainer List
Fedora Extras Quality Assurance
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Depends On:
Blocks:
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Reported: 2010-05-12 05:43 EDT by Andre Przywara
Modified: 2010-06-03 04:06 EDT (History)
7 users (show)

See Also:
Fixed In Version: 2.6.33.4-95
Doc Type: Bug Fix
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Last Closed: 2010-05-20 23:49:17 EDT
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Description Andre Przywara 2010-05-12 05:43:30 EDT
Description of problem:
AMD's Six-Core processor have a Turbo-Core feature automatically activated without software involvement. Due to a conflict with the powernow-k8 driver this feature is not activated under recent Linux kernel versions, resulting in bad performance.

Version-Release number of selected component (if applicable):
all Linux kernels starting from 2.6.30, including the Fedora13 version

How reproducible:
Do performance testing with AMD's desktop Six-Core processors featuring Turbo-Core (PhenomII X6 1090T and 1055T). Compare the performance to that with the Cool'n'Quiet _disabled_ in the BIOS.

Steps to Reproduce:
1. Boot Fedora13 on an AMD PhenomII X6 processor
2. Do some performance testing
3. Disable Cool'n'Quiet feature in the BIOS
4. Repeat performance testing, compare numbers to that of Step2
  
Actual results:
Performance with C'n'Q enabled is worse than with C'n'Q disabled.

Expected results:
Performance with C'n'Q enabled should be equal or better compared to C'n'Q disabled.

Additional info:
Following online articles describe the problem:
http://www.h-online.com/open/news/item/Performance-problem-in-AMD-s-Phenom-II-X6-under-Linux-993127.html
http://www.linux-magazine.com/Online/News/Phenom-II-X6-Performance-Under-Linux-Below-Expectations
Comment 1 Andre Przywara 2010-05-12 05:48:46 EDT
The appropriate fix (a one-liner):
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=b810e94c9d8e3fff6741b66cd5a6f099a7887871
is already in 2.6.34-rc7 and will trickle down into stable soon.
Please cherry-pick this one into the Fedora13 release kernel.

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