Memory used to be homogeneous. Then NUMA came along. Later different types of memory (persistent memory, on-package high bandwidth memory, CXL attached memory). Each type of memory has its own performance characteristics, and users will need to monitor and control access by type. The MRRM solution is to tag physical address ranges with "region IDs" so that platform firmware[1] can indicate the type of memory for each range (with separate tags available for local vs. remote access to each range). Note that these ranges can include addresses reserved for future hotplugged memory. The region IDs will be used to provide separate event counts for each region for "perf" and for the "resctrl" file system to monitor and control memory bandwidth in each region. Users will need to know the address range(s) that are part of each region. This patch series adds /sys/firmware/acpi/memory_ranges/rangeX directories to provide user space accessible enumeration. -Tony [1] MRRM definition allow for future expansion for the OS to assign these region IDs. Changes since version 3 here: https://lore.kernel.org/all/20250410223207.257722-1-tony.luck@xxxxxxxxx/ 1) Rebase to v6.15-rc4 2) Removed ugly #ifdef in acpi_mrrm.c with better fix for CONFIG_NUMA=n 3) Moved stub for acpi_mrrm_max_mem_region() into #else !ACPI section of <linux/acpi.h> Tony Luck (4): ACPICA: Define MRRM ACPI table ACPI/MRRM: Minimal parse of ACPI MRRM table ACPI/MRRM: Add /sys files to describe memory ranges ACPI: Add documentation for exposing MRRM data include/linux/acpi.h | 9 + include/acpi/actbl1.h | 7 + include/acpi/actbl2.h | 42 ++++ drivers/acpi/acpi_mrrm.c | 183 ++++++++++++++++++ Documentation/ABI/testing/sysfs-firmware-acpi | 21 ++ arch/x86/Kconfig | 1 + drivers/acpi/Kconfig | 3 + drivers/acpi/Makefile | 1 + 8 files changed, 267 insertions(+) create mode 100644 drivers/acpi/acpi_mrrm.c base-commit: b4432656b36e5cc1d50a1f2dc15357543add530e -- 2.48.1
