Intel Performance Limit Reasons For Linux To Report Why Your CPU Is Downclocking

Written by Michael Larabel in Intel on 27 May 2024 at 01:23 PM EDT. 14 Comments
Intel Performance Limit Reasons (PLR) can indicate why your CPU is downclocking / limited to a lower performance limit for a given core or die. With some Windows utilities this information this Intel CPU feature has been available there while now Intel is bringing PLR support to Linux too.

Intel Performance Limit Reasons can report why the performance/power is being limited at the die level or for individual CPU cores within a die. With a new set of patches today to the Linux kernel mailing list, Intel PLR hardware performance event reporting is being wired up. The information is they conveyed to user-space via DebugFS for administrators to tap into directly or for other applications wanting to know why their CPU performance may be limited.

Intel Performance Limit Reasons

With the proposed Linux patches for Intel Performance Limit Reasons, the information is conveyed via /sys/kernel/debug/tpmi-*/plr/domain*/status. But as typical with DebugFS, "/sys/kernel/debug/" is typically restricted to software with root/administrator privileges.

With these patches there is a new "INTEL_PLR_TPMI" Kconfig option for gating this Intel PLR driver. Hopefully everything will be in shape for getting it mainlined in Linux v6.11. Those interested in the Intel PLR functionality can find the new driver patches for now on the kernel mailing list.
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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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