qcom_l3_pmu.rst 1.4 KB

1234567891011121314151617181920212223242526
  1. ===========================================================================
  2. Qualcomm Datacenter Technologies L3 Cache Performance Monitoring Unit (PMU)
  3. ===========================================================================
  4. This driver supports the L3 cache PMUs found in Qualcomm Datacenter Technologies
  5. Centriq SoCs. The L3 cache on these SOCs is composed of multiple slices, shared
  6. by all cores within a socket. Each slice is exposed as a separate uncore perf
  7. PMU with device name l3cache_<socket>_<instance>. User space is responsible
  8. for aggregating across slices.
  9. The driver provides a description of its available events and configuration
  10. options in sysfs, see /sys/devices/l3cache*. Given that these are uncore PMUs
  11. the driver also exposes a "cpumask" sysfs attribute which contains a mask
  12. consisting of one CPU per socket which will be used to handle all the PMU
  13. events on that socket.
  14. The hardware implements 32bit event counters and has a flat 8bit event space
  15. exposed via the "event" format attribute. In addition to the 32bit physical
  16. counters the driver supports virtual 64bit hardware counters by using hardware
  17. counter chaining. This feature is exposed via the "lc" (long counter) format
  18. flag. E.g.::
  19. perf stat -e l3cache_0_0/read-miss,lc/
  20. Given that these are uncore PMUs the driver does not support sampling, therefore
  21. "perf record" will not work. Per-task perf sessions are not supported.