The 50 Watt Power Regression Is Believed To Be Fixed
Written by Michael Larabel in Linux Kernel on 31 December 2013 at 12:38 AM EST. 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.

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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter or contacted via

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