CPUsNews

Intel Alder Lake-S CPUs will Allow Disabling of Low-Power or High-Performance Cores

A new Linux kernel update indicates that users will be able to disable one of the type of cores (low-power or high-performance) in the next-gen Alder Lake-S CPUs for better load balancing with legacy applications and games that aren’t able to distinguish between the two. The CPU can be turned from a heterogeneous to a homogeneous core by disabling one type of cores from the command line or the BIOS.

Another reason for disabling the low-performance cores is to allow support for AVX-512 instructions which are only supported on the Sunny/Willow/Golden Cove cores and not the Monts. However, it’s worth not that disabling the low-power cores will significantly reduce the overall compute performance as Grace Mont is more or less on par with Sky Lake and will constitute roughly half of the overall core count.

Alder Lake Hybrid system has two different types of core, Golden Cove
core and Gracemont core. The Golden Cove core is registered to
"cpu_core" PMU. The Gracemont core is registered to "cpu_atom" PMU.

The difference between the two PMUs include:
- Number of GP and fixed counters
- Events
- The "cpu_core" PMU supports Topdown metrics.
  The "cpu_atom" PMU supports PEBS-via-PT.

The "cpu_core" PMU is similar to the Sapphire Rapids PMU, but without
PMEM.
The "cpu_atom" PMU is similar to Tremont, but with different events,
event_constraints, extra_regs and number of counters.

The mem-loads AUX event workaround only applies to the Golden Cove core.

Users may disable all CPUs of the same CPU type on the command line or
in the BIOS. For this case, perf still register a PMU for the CPU type
but the CPU mask is 0.

Current caps/pmu_name is usually the microarch codename. Assign the
"alderlake_hybrid" to the caps/pmu_name of both PMUs to indicate the
hybrid Alder Lake microarchitecture.

Source

Areej

Computer Engineering dropout (3 years), writer, journalist, and amateur poet. I started my first technology blog, Techquila while in college to address my hardware passion. Although largely successful, it was a classic example of too many people trying out multiple different things but getting nothing done. Left in late 2019 and been working on Hardware Times ever since.

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