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AMD Engineer Details Zen 6 IBS Memory Profiler

What happened

AMD has detailed the IBS Memory Profiler, a little-discussed hardware feature in its upcoming Zen 6 processors. AMD engineer Bharata Bhasker Rao presented it at the Linux Plumbers Conference (LPC) 2026 in Prague on October 5. Instruction-Based Sampling (IBS) is AMD's existing profiling hardware, and Zen 6 adds a separate, lighter instance that only samples data memory accesses; each sample hands the kernel the physical address of the access and shows whether the data came from DRAM or external memory such as CXL. AMD's EPYC 9006 "Venice" chips support memory expansion via CXL 3.1. AMD wants to feed the profiler's samples into pghot, a proposed kernel subsystem for hot page tracking; the pghot patches are still in development. The results are a mixed bag: on a test system with 256 logical CPUs and 256 GB of CXL memory, XSBench ran at 4.57x over a no-tiering baseline against 1.18x for the current method, and Graph500 hit 3.17x against 2.34x; Redis saw no gain and NAS BT landed slightly behind. Per-folio promotion cost fell from 26.1 to 15.8 microseconds in an overhead test, though that benchmark finished about 5% slower. These are AMD's own numbers, and the slides list no virtualization support for the profiler. EPYC Venice is in production, with cloud deployments expected later this year.