HMEM Device Driver Coming For Linux 5.5

Intel's HMEM DAX driver is being added to Linux 5.5 for use-cases like their Optane DC Persistent Memory.

With devices like Intel Optane DC Persistent Memory and others coming to market that offer different tiers of performance compared to conventional system memory, the HMEM driver is used for interfacing with EFI/ACPI platform firmware for reading these different memory ranges and their performance classes to handle these different memory pools appropriately.

With the higher performance memory ranges, they may be reserved for application-specific use-cases like databases as opposed to just being part of the conventional system RAM pool. The HMEM driver with Linux 5.5 allows for assigning that specialized memory capacity to a device-DAX (direct access) memory map (mmap) instance by default. The KMEM driver meanwhile allows already the DAX device to be assigned to the core memory management / system RAM pool if not desiring the application-specific handling.

More details via the HMEM driver patch being queued as part of the ACPI / power management tree ahead of the upcoming Linux 5.5 merge window.