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The 50 Watt Power Regression Is Believed To Be Fixed

Linux Kernel

Published on 31 December 2013 12:38 AM EST
Written by Michael Larabel in Linux Kernel
1 Comment

Near the beginning of the month I wrote about an Intel developer finding a Linux kernel power regression increasing the system's power use by 50 Watts. After extensive testing and investigating, the issue has been fixed ahead of the Linux 3.13 kernel release and is proposed for stable point releases on the 3.10, 3.11, and 3.12 kernels.

As was anticipated by Intel's Len Brown, the kernel power regression that went into the Linux 3.10 kernel and went unnoticed until Linux 3.13 development is due to excessive wake-ups with cpuidle.

The fix for this issue ended up being an Intel errata workaround that originally just covered Intel's Core 2 "Dunnington" platform to be extended to the Nehalem EX and Westmere EX platforms too.

The change drops the idle power use on these platforms and it's believed at this time the issue only affects the Nehalem EX and Westmere EX platforms. The commit was merged to mainline a number of days ago and can be found with this simple Git commit -- only five lines of code had to be changed.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
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