Intel Broadwell-U P-State vs. ACPI CPUFreq Scaling Linux Performance
Written by Michael Larabel in Intel on 28 January 2015 at 09:28 AM EST. 12 Comments
INTEL --
As some extra Broadwell Linux performance numbers this morning, here's some brief test results for the Intel Core i7 5600U when testing the Intel P-State vs. ACPI CPUFreq frequency scaling drivers and the different scaling governors.

While not as in-depth as some of my past P-State CPU frequency scaling driver testing, for those curious whether CPUFreq vs. P-State drivers make a difference for Broadwell ultrabooks, I ran some basic performance tests on my Lenovo ThinkPad X1 Carbon with i7-5600U. With CPUFreq and P-State I also tested the basic available scaling governors. More thorough Broadwell scaling testing will come -- and also looking at the thermal and power consumption when having some more powerful Broadwell CPUs in my possession along with more time to carry out the tests. Just look at today's one-page results as some preliminary figures since as you'll see there wasn't too much to look at with these numbers.

The new Lenovo ThinkPad was tested with Ubuntu 15.04 on the Linux 3.18 kernel. Tested were Intel P-State Powersave, P-State Performance, CPUFreq Performance, and CPUFreq Ondemand (contrary to the system table) for this dual-core CPU with Hyper Threading. The i7-5600U's maximum turbo frequency is 3.2GHz while the non-turbo frequency is 2.6GHz. P-State powersave was the default mode of operation for the Linux kernel versions tested thus far on the Intel ultrabook.

Those wanting to see these rather flat results can view them via 1501259-DE-INTELCPUB60 on OpenBenchmarking.org. Feel free to comment on this article and share what your latest experiences have been when tweaking the CPU frequency scaling driver/governor on modern kernel releases; for some hardware, this can still make a big impact in performance though kernel developers have been trying to iron out some of the past regressions.
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Michael Larabel is the principal author of Phoronix.com 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 OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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