1.. SPDX-License-Identifier: GPL-2.0 2 3====================================== 4CXL Performance Monitoring Unit (CPMU) 5====================================== 6 7The CXL rev 3.0 specification provides a definition of CXL Performance 8Monitoring Unit in section 13.2: Performance Monitoring. 9 10CXL components (e.g. Root Port, Switch Upstream Port, End Point) may have 11any number of CPMU instances. CPMU capabilities are fully discoverable from 12the devices. The specification provides event definitions for all CXL protocol 13message types and a set of additional events for things commonly counted on 14CXL devices (e.g. DRAM events). 15 16CPMU driver 17=========== 18 19The CPMU driver registers a perf PMU with the name pmu_mem<X>.<Y> on the CXL bus 20representing the Yth CPMU for memX. 21 22 /sys/bus/cxl/device/pmu_mem<X>.<Y> 23 24The associated PMU is registered as 25 26 /sys/bus/event_sources/devices/cxl_pmu_mem<X>.<Y> 27 28In common with other CXL bus devices, the id has no specific meaning and the 29relationship to specific CXL device should be established via the device parent 30of the device on the CXL bus. 31 32PMU driver provides description of available events and filter options in sysfs. 33 34The "format" directory describes all formats of the config (event vendor id, 35group id and mask) config1 (threshold, filter enables) and config2 (filter 36parameters) fields of the perf_event_attr structure. The "events" directory 37describes all documented events show in perf list. 38 39The events shown in perf list are the most fine grained events with a single 40bit of the event mask set. More general events may be enable by setting 41multiple mask bits in config. For example, all Device to Host Read Requests 42may be captured on a single counter by setting the bits for all of 43 44* d2h_req_rdcurr 45* d2h_req_rdown 46* d2h_req_rdshared 47* d2h_req_rdany 48* d2h_req_rdownnodata 49 50Example of usage:: 51 52 $#perf list 53 cxl_pmu_mem0.0/clock_ticks/ [Kernel PMU event] 54 cxl_pmu_mem0.0/d2h_req_rdshared/ [Kernel PMU event] 55 cxl_pmu_mem0.0/h2d_req_snpcur/ [Kernel PMU event] 56 cxl_pmu_mem0.0/h2d_req_snpdata/ [Kernel PMU event] 57 cxl_pmu_mem0.0/h2d_req_snpinv/ [Kernel PMU event] 58 ----------------------------------------------------------- 59 60 $# perf stat -a -e cxl_pmu_mem0.0/clock_ticks/ -e cxl_pmu_mem0.0/d2h_req_rdshared/ 61 62Vendor specific events may also be available and if so can be used via 63 64 $# perf stat -a -e cxl_pmu_mem0.0/vid=VID,gid=GID,mask=MASK/ 65 66The driver does not support sampling so "perf record" is unsupported. 67It only supports system-wide counting so attaching to a task is 68unsupported. 69