Intel's Patches Discussed For Exposing Hybrid CPU Topology Via Sysfs
Written by Michael Larabel in Intel on 6 October 2020 at 06:50 AM EDT. 5 Comments
INTEL --
Last week open-source developers at Intel began sending out Linux patches for supporting hybrid CPUs particularly ahead of 12th Gen "Alder Lake" coming to market with a mix of Golden Cove and Gracemont cores. Following that article last week, more patches hit the list in exposing the hybrid CPU topology to user-space.

These patches indicate how Intel plans to expose the hybrid CPU topology to user-space for software interested in the core make-up of the system. While Arm devices on Linux in big.LITTLE designs expose their details via /sys/devices/system/cpu/cpuX/cpu_capacity, Intel is planning to expose a separate and brand new interface via /sys/devices/system/cpu/types.

Within /sys/devices/system/cpu/types the plan is to have a separate sub-directory for each type of CPU core present on the system and within there will be a CPU list and map that user-space can query for finding out which cores are of what microarchitecture and any other pressing attributes. Intel engineers feel this interface is better as from one read it can then be determined what cores are of a given type compared to the cpu_capacity approach with Arm where a file needs to be read for each core. The proposed Intel hybrid sysfs patches can be found via the LKML.

However, Linux kernel veteran Greg Kroah-Hartman has so far had some critiques to the design as well as suggesting better cooperation with Arm engineers in related patches. So we'll see ahead how the patches evolve, but given Alder Lake won't be out until at least towards the end of next year, there still is plenty of time to revise this work.
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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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