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Documentation: fpga: dfl: add description for performance reporting support

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This patch adds description for performance reporting support for
Device Feature List (DFL) based FPGA.

Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Wu Hao <hao.wu@intel.com>
Link: https://lore.kernel.org/r/1587949583-12058-2-git-send-email-hao.wu@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Xu Yilun 2020-04-27 09:06:22 +08:00 committed by Greg Kroah-Hartman
parent a2cc220a9a
commit 1f03ac9460
1 changed files with 84 additions and 0 deletions
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Documentation/fpga/dfl.rst
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@ -118,6 +118,11 @@ More functions are exposed through sysfs
management information (current temperature, thresholds, threshold status,
etc.).
Performance reporting
performance counters are exposed through perf PMU APIs. Standard perf tool
can be used to monitor all available perf events. Please see performance
counter section below for more detailed information.
FIU - PORT
==========
@ -378,6 +383,85 @@ The device nodes used for ioctl() or mmap() can be referenced through::
/sys/class/fpga_region/<regionX>/<dfl-port.n>/dev
Performance Counters
====================
Performance reporting is one private feature implemented in FME. It could
supports several independent, system-wide, device counter sets in hardware to
monitor and count for performance events, including "basic", "cache", "fabric",
"vtd" and "vtd_sip" counters. Users could use standard perf tool to monitor
FPGA cache hit/miss rate, transaction number, interface clock counter of AFU
and other FPGA performance events.
Different FPGA devices may have different counter sets, depending on hardware
implementation. E.g., some discrete FPGA cards don't have any cache. User could
use "perf list" to check which perf events are supported by target hardware.
In order to allow user to use standard perf API to access these performance
counters, driver creates a perf PMU, and related sysfs interfaces in
/sys/bus/event_source/devices/dfl_fme* to describe available perf events and
configuration options.
The "format" directory describes the format of the config field of struct
perf_event_attr. There are 3 bitfields for config: "evtype" defines which type
the perf event belongs to; "event" is the identity of the event within its
category; "portid" is introduced to decide counters set to monitor on FPGA
overall data or a specific port.
The "events" directory describes the configuration templates for all available
events which can be used with perf tool directly. For example, fab_mmio_read
has the configuration "event=0x06,evtype=0x02,portid=0xff", which shows this
event belongs to fabric type (0x02), the local event id is 0x06 and it is for
overall monitoring (portid=0xff).
Example usage of perf::
$# perf list |grep dfl_fme
dfl_fme0/fab_mmio_read/ [Kernel PMU event]
<...>
dfl_fme0/fab_port_mmio_read,portid=?/ [Kernel PMU event]
<...>
$# perf stat -a -e dfl_fme0/fab_mmio_read/ <command>
or
$# perf stat -a -e dfl_fme0/event=0x06,evtype=0x02,portid=0xff/ <command>
or
$# perf stat -a -e dfl_fme0/config=0xff2006/ <command>
Another example, fab_port_mmio_read monitors mmio read of a specific port. So
its configuration template is "event=0x06,evtype=0x01,portid=?". The portid
should be explicitly set.
Its usage of perf::
$# perf stat -a -e dfl_fme0/fab_port_mmio_read,portid=0x0/ <command>
or
$# perf stat -a -e dfl_fme0/event=0x06,evtype=0x02,portid=0x0/ <command>
or
$# perf stat -a -e dfl_fme0/config=0x2006/ <command>
Please note for fabric counters, overall perf events (fab_*) and port perf
events (fab_port_*) actually share one set of counters in hardware, so it can't
monitor both at the same time. If this set of counters is configured to monitor
overall data, then per port perf data is not supported. See below example::
$# perf stat -e dfl_fme0/fab_mmio_read/,dfl_fme0/fab_port_mmio_write,\
portid=0/ sleep 1
Performance counter stats for 'system wide':
3 dfl_fme0/fab_mmio_read/
<not supported> dfl_fme0/fab_port_mmio_write,portid=0x0/
1.001750904 seconds time elapsed
The driver also provides a "cpumask" sysfs attribute, which contains only one
CPU id used to access these perf events. Counting on multiple CPU is not allowed
since they are system-wide counters on FPGA device.
The current driver does not support sampling. So "perf record" is unsupported.
Add new FIUs support
====================
It's possible that developers made some new function blocks (FIUs) under this