ARM DynamIQ Shared Unit (DSU) PMU — The Linux Kernel 5.18.5-gnu-1 documentation

# ARM DynamIQ Shared Unit (DSU) PMU

ARM DynamIQ Shared Unit integrates one or more cores with an L3 memory system, control logic and external interfaces to form a multicore cluster. The PMU allows counting the various events related to the L3 cache, Snoop Control Unit etc, using 32bit independent counters. It also provides a 64bit cycle counter.

The PMU can only be accessed via CPU system registers and are common to the cores connected to the same DSU. Like most of the other uncore PMUs, DSU PMU doesn’t support process specific events and cannot be used in sampling mode.

The DSU provides a bitmap for a subset of implemented events via hardware registers. There is no way for the driver to determine if the other events are available or not. Hence the driver exposes only those events advertised by the DSU, in “events” directory under:

    /sys/bus/event_sources/devices/arm_dsu_<N>/

The user should refer to the TRM of the product to figure out the supported events and use the raw event code for the unlisted events.

The driver also exposes the CPUs connected to the DSU instance in “associated_cpus”.

e.g usage:

    perf stat -a -e arm_dsu_0/cycles/