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- .. SPDX-License-Identifier: GPL-2.0
- ======================================
- CXL Performance Monitoring Unit (CPMU)
- ======================================
- The CXL rev 3.0 specification provides a definition of CXL Performance
- Monitoring Unit in section 13.2: Performance Monitoring.
- CXL components (e.g. Root Port, Switch Upstream Port, End Point) may have
- any number of CPMU instances. CPMU capabilities are fully discoverable from
- the devices. The specification provides event definitions for all CXL protocol
- message types and a set of additional events for things commonly counted on
- CXL devices (e.g. DRAM events).
- CPMU driver
- ===========
- The CPMU driver registers a perf PMU with the name pmu_mem<X>.<Y> on the CXL bus
- representing the Yth CPMU for memX.
- /sys/bus/cxl/device/pmu_mem<X>.<Y>
- The associated PMU is registered as
- /sys/bus/event_sources/devices/cxl_pmu_mem<X>.<Y>
- In common with other CXL bus devices, the id has no specific meaning and the
- relationship to specific CXL device should be established via the device parent
- of the device on the CXL bus.
- PMU driver provides description of available events and filter options in sysfs.
- The "format" directory describes all formats of the config (event vendor id,
- group id and mask) config1 (threshold, filter enables) and config2 (filter
- parameters) fields of the perf_event_attr structure. The "events" directory
- describes all documented events show in perf list.
- The events shown in perf list are the most fine grained events with a single
- bit of the event mask set. More general events may be enable by setting
- multiple mask bits in config. For example, all Device to Host Read Requests
- may be captured on a single counter by setting the bits for all of
- * d2h_req_rdcurr
- * d2h_req_rdown
- * d2h_req_rdshared
- * d2h_req_rdany
- * d2h_req_rdownnodata
- Example of usage::
- $#perf list
- cxl_pmu_mem0.0/clock_ticks/ [Kernel PMU event]
- cxl_pmu_mem0.0/d2h_req_rdshared/ [Kernel PMU event]
- cxl_pmu_mem0.0/h2d_req_snpcur/ [Kernel PMU event]
- cxl_pmu_mem0.0/h2d_req_snpdata/ [Kernel PMU event]
- cxl_pmu_mem0.0/h2d_req_snpinv/ [Kernel PMU event]
- -----------------------------------------------------------
- $# perf stat -a -e cxl_pmu_mem0.0/clock_ticks/ -e cxl_pmu_mem0.0/d2h_req_rdshared/
- Vendor specific events may also be available and if so can be used via
- $# perf stat -a -e cxl_pmu_mem0.0/vid=VID,gid=GID,mask=MASK/
- The driver does not support sampling so "perf record" is unsupported.
- It only supports system-wide counting so attaching to a task is
- unsupported.
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