Queued Linux Patches To Better Track AVX-512, Allowing For More Optimal Task Placement
Written by Michael Larabel in Intel on 12 February 2019 at 06:16 AM EST. 9 Comments
INTEL --
After going through several rounds of patch review in recent months, a patch series providing for tracking AVX-512 usage of tasks and exporting it to user-space is poised to be part of the upcoming Linux 5.1 kernel.

As using complex AVX-512 operations can lead to lower turbo frequencies for those cores, the Linux kernel will be providing better tracking of AVX-512 usage of tasks that is readable by user-space for programs doing their own task placement. If keeping AVX-512 usage to particular core(s) and not intermixing them with non-AVX tasks, better performance can be achievable due to the differing turbo frequencies of CPUs when running Advanced Vector Extensions.

This patch to track AVX-512 usage of tasks is now queued in the x86/fpu Git branch ahead of the Linux 5.1 cycle.

Separately there are also patches pending to expose the AVX-512 usage elapsed time via the /proc/pid/status with a new AVX512_elapsed_ms metric that provides a hint whether AVX-512 was ever used by that process and if so roughly how long ago.

This AVX-512 usage tracking is said to be useful for real-world workloads like TensorFlow and Linpack but no performance details were shared to quantify the impact.

With expanded AVX-512 rolling out to more processors with Icelake later this year, the timing is good for getting these additional bits into the kernel. AVX-512 is supported by current Skylake-X and Xeon Scalable processors as well as Xeon Phi and friends.
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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 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 OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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