Linux load balancing mechanism still needs to better adapt to Intel hybrid architecture processors
Linux load balancing mechanism still needs to better adapt to Intel hybrid architecture processors.
In the past year since the introduction of Intel’s Alder Lake processors, Intel engineers have made several improvements to the Linux kernel to better handle mixed P-core and E-core processing methods.
While Alder Lake has worked well in recent versions of the kernel, and the task selection for P and E cores on Linux is more complete than it was at launch, Intel engineers this week raised areas for improvement.
Last week, the important Linux kernel patch series was released to work on “task classes” for mixed CPUs and proper implementation of thread management support on Linux.
This week, the Linux Plumbers Conference also brought up the topic of how to adapt Linux’s energy-conscious scheduling to Intel’s hybrid CPUs, since EAS is now only tailored for Arm big.LITTLE designs.
At this week’s LPC2022 conference, Intel engineers Zhang Rui and Chen Yu mentioned that Intel’s work on hybrid Linux still needs to be refined.
This additional statement is to suggest that the Linux kernel’s load balancing mechanism is still not satisfactory for Intel’s hybrid processors.
In particular, the frequency maximum used to calculate the frequency scale is a global value and not specific to different types of cores, since P cores and E cores have different maximum frequency values during operation.
The frequency max value can also not be correctly judged based on turbo mode, thermal/power throttling, etc., and the max frequency value cannot be adjusted at runtime.
Those interested in this topic can find the full slideshow at the address below outlining the current Linux load balancing issues with Intel hybrid CPUs and possible improvements.