| Agustin Vega-Frias | 3071f13 | 2017-03-31 14:13:43 -0400 | [diff] [blame] | 1 | Qualcomm Datacenter Technologies L3 Cache Performance Monitoring Unit (PMU) |
| 2 | =========================================================================== |
| 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 | |
| 10 | The driver provides a description of its available events and configuration |
| 11 | options in sysfs, see /sys/devices/l3cache*. Given that these are uncore PMUs |
| 12 | the driver also exposes a "cpumask" sysfs attribute which contains a mask |
| 13 | consisting of one CPU per socket which will be used to handle all the PMU |
| 14 | events on that socket. |
| 15 | |
| 16 | The hardware implements 32bit event counters and has a flat 8bit event space |
| 17 | exposed via the "event" format attribute. In addition to the 32bit physical |
| 18 | counters the driver supports virtual 64bit hardware counters by using hardware |
| 19 | counter chaining. This feature is exposed via the "lc" (long counter) format |
| 20 | flag. E.g.: |
| 21 | |
| 22 | perf stat -e l3cache_0_0/read-miss,lc/ |
| 23 | |
| 24 | Given that these are uncore PMUs the driver does not support sampling, therefore |
| 25 | "perf record" will not work. Per-task perf sessions are not supported. |