Linux Continues Prepping EFI Special Purpose Memory Support
Written by Michael Larabel in Hardware on 31 May 2019 at 04:39 AM EDT. 1 Comment
HARDWARE --
With hardware these days from Intel Optane DC Persistent Memory to HBM being stacked on chips for specialized use-cases, the Linux kernel has been preparing support for the new EFI Special/Specific Purpose Memory specification for knowing about such specialized memory use-cases it shouldn't be treating as normal RAM.

EFI Special Memory (EFI_MEM_SP) succeeds the earlier ACPI HMAT (Heterogeneous Memory Attribute Table) for indicating if a memory pool is general purpose memory or intended for application-specific usage. If it is and the kernel obeys this new attribute, the kernel will avoid allocating to that region and reserve it for use by applications specifically looking for this specialized memory. For the most part it's intended for cases like HBM (High Bandwidth Memory) on a chip that may be addressable by the system itself but given its performance heuristics and limited capacity should be reserved for application-specific purposes rather than inadvertently being used by the kernel for mundane memory storage.

Intel developers have been busy in working on this EFI Specific/Special Purpose Memory support and the latest patches were posted on Thursday, which ride off the Linux 5.2's HMAT/HMEM_REPORTING code. More details via this patch series. With more interesting hardware hitting the market soon and likely supporting this EFI specification, hopefully the code will make it into Linux 5.3.
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Michael Larabel is the principal author of Phoronix.com 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 OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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