Re: [PATCH v5 5/5] docs: perf: Minimal introduction the the CXL PMU device and driver

[Liang, Kan]

On 2023-04-11 2:54 p.m., Jonathan Cameron wrote:
> Very basic introduction to the device and the current driver support
> provided. I expect to expand on this in future versions of this patch
> set.
> 
> Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> 


Reviewed-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>

Thanks,
Kan
> --
> v5:
> - Correct final statemnt about sampling support. (Kan)
> - Update CXL PMU MAINTAINERS entry to include this documentation
> - Update device naming to cxl_pmu_memX.Y etc
> ---
>  Documentation/admin-guide/perf/cxl.rst   | 68 ++++++++++++++++++++++++
>  Documentation/admin-guide/perf/index.rst |  1 +
>  MAINTAINERS                              |  1 +
>  3 files changed, 70 insertions(+)
> 
> diff --git a/Documentation/admin-guide/perf/cxl.rst b/Documentation/admin-guide/perf/cxl.rst
> new file mode 100644
> index 000000000000..2a1c684603bb
> --- /dev/null
> +++ b/Documentation/admin-guide/perf/cxl.rst
> @@ -0,0 +1,68 @@
> +.. 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 -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 -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.
> diff --git a/Documentation/admin-guide/perf/index.rst b/Documentation/admin-guide/perf/index.rst
> index 9de64a40adab..f60be04e4e33 100644
> --- a/Documentation/admin-guide/perf/index.rst
> +++ b/Documentation/admin-guide/perf/index.rst
> @@ -21,3 +21,4 @@ Performance monitor support
>     alibaba_pmu
>     nvidia-pmu
>     meson-ddr-pmu
> +   cxl
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 51234eb7858e..29a108afa065 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5178,6 +5178,7 @@ COMPUTE EXPRESS LINK PMU (CPMU)
>  M:	Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>
>  L:	linux-cxl@xxxxxxxxxxxxxxx
>  S:	Maintained
> +F:	Documentation/admin-guide/perf/cxl.rst
>  F:	drivers/perf/cxl_pmu.c
>  
>  CONEXANT ACCESSRUNNER USB DRIVER