A Power/Performance Optimization Is On The Way For POWER Linux Users
Written by Michael Larabel in Hardware on 7 April 2019 at 08:41 AM EDT. Add A Comment
HARDWARE --
For those currently using a Raptor Talos II or awaiting the Raptor Blackbird or are running another IBM POWER system like the recently covered cheap POWER servers, there is a CPU Idle patch-set on the way that helps improve the power/performance.

A Phoronix reader pointed out an interesting patch series this week that is to the Linux kernel's CPU Idle code and specifically should help out IBM POWER processors due to tweaking the auto-promotion logic for CPU idle states.

Here's the juicy bit: "We are able to get out of stop0_lite generally in 150us (with this patch) as compared to 4ms(with tick retained). As stated earlier, we do not want to get stuck into stop0_lite as it inhibits SMT folding for other sibling threads, depriving them of core resources. Current patch is using auto-promotion only for stop0_lite, as it gives performance benefit (primary reason) along with lowering down power consumption. We may extend this model for other states in future."

No hard numbers were provided for the power/performance benefits, but once this work is merged (presumably with Linux 5.2), I'll run some fresh benchmarks on the Raptor Talos II.

More details in the patch series.
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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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