Arm Brings TLBID to Linux to Boost High-Core-Count CPUs

Arm this week sent out an initial set of patches that add support for TLBI Domains to the Linux kernel. Branded "TLBID," it is an upcoming Arm architecture capability aimed at improving performance on systems with a large number of cores.

What it does

TLBID makes it possible to perform Translation Lookaside Buffer (TLB) invalidation on just a subset of CPU cores rather than across the whole system. Today a TLB flush typically hits every processor, which becomes costly on highly parallel machines.

The developers are wiring up the kernel so that TLB invalidation commands go only to the cores where a given process was actually running, avoiding the need to clear the TLB system-wide. That should be especially helpful for high-core-count Arm server processors.

When to expect it

No performance figures have been shared yet. On top of that, TLBID is not yet part of the Arm Architecture Reference Manual, so it will likely be a while before it shows up in silicon.

Beyond the kernel patches, ARM64 TLBID support also depends on the right toolchain: LLVM 23 or newer, or GNU Binutils 2.46 or newer, which provide the necessary instruction support.

Those curious about the TLBID effort for future Arm designs can follow it on the Linux kernel mailing list.

Source: Phoronix