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