Linux 4.5 Appears To Slightly Lower Power Use, But Linux 4.6 Will Be Even Better

Written by Michael Larabel in Linux Kernel on 12 March 2016 at 08:00 AM EST. 10 Comments
With Linux 4.5 expected this weekend, I've been running some more, one-off tests of this new kernel. One of the latest test runs was looking at the power use of the kernel on an Intel Haswell ultrabook.

From an ASUS Zenbook (UX301LAA) with Core i7 Haswell CPU I ran some power monitoring tests of the battery when running Linux 4.4 stable on Ubuntu 16.04, Linux 4.5 Git, and also the Linux 4.6 Intel DRM-Next code (since for Linux 4.6 there is FBC and PSR enabled by default).
Linux 4.5 Kernel Power Use

Everything else remained the same during testing... First up is just when idling from the Ubuntu-based ultrabook/laptop:
Linux 4.5 Kernel Power Use

Linux 4.5 is lower than Linux 4.4 across the board compared to Linux 4.4. However, when pulling down the DRM-Next code for Linux 4.6, the results get even better! Linux 4.5's power use dropped by about 9% compared to 4.4 and Linux 4.6 looks like it could drop this system's power use by another 10~13%. That is if Intel doesn't end up having to disable Frame-Buffer Compression again like they have in the past due to regressions.
Linux 4.5 Kernel Power Use

Along with lowering the power use, the CPU remains cooler on the newer kernels. The idle data can be found via this result file.
Linux 4.5 Kernel Power Use

The Linux 4.5/4.6 benefits though are namely when idling. Under load, there isn't much difference in the results.
Linux 4.5 Kernel Power Use
You can look at the load data via this result file. If there is enough reader interest, I can carry out some Linux 4.5 / 4.6 DRM-Next power tests on a few other Intel laptops/ultrabooks; let me know via the forums or on Twitter.
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Michael Larabel

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 20,000 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, LinkedIn, or contacted via

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