Intel TPEBS & LBR Event Logging Supported By Linux 6.12 With Perf Tools

The perf tooling changes were merged today for the in-development Linux 6.12 kernel. Notable on the perf tools side is supporting some features found in newer Intel processors.

The perf tools with Linux 6.12 add Intel branch counters support using LBR event logging. The Last Branch Record (LBR) event logging allows for logging PMU event data within LBRs.

This LBR Event Logging support is first found with Intel Xeon 6 "Sierra Forest" and upcoming Grand Ridge processors. Grand Ridge and Sierra Forest feature Crestmont E cores but over the incarnation found within Meteor Lake there is now this PMU LBR event logging capability. The Intel documentation with the patches goes on to explain of the LBR event logging:

"The LBR event logging introduces a per-counter indication of precise event occurrences in LBRs. It can provide a means to attribute exposed retirement latency to combinations of events across a block of instructions. It also provides a means of attributing Timed LBR latencies to events."

The other new Intel CPU feature with the perf tools work for Linux 6.12 is supporting Timed PEBS, or Precision Event-Based Sampling. With the perf stat command the new "--enable-tpebs-recording" option can be used for enabling Timed PEBS (TPEBS). More details on Timed PEBS as found with Meteor Lake and Granite Rapids can be found via this Intel.com documentation.

Also on the Intel side with Linux 6.12 perf tools is updating the Meteor Lake metric JSON files for perf events.

Linux 6.12 per tools also allows using BPF+BTF to collect and print syscall and tracepoint arguments within "perf trace", various data type profiling improvements, and more. See the Git merge for the full list of perf tools feature changes this cycle.