samples: profiling: Add sample for perf tool

The operation of perf tool can be checked using this sample.

Signed-off-by: Mikhail Kushnerov <[email protected]>

Author: Mikhail Kushnerov

samples/subsys/profiling/perf/CMakeLists.txt

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+# Copyright (c) 2023 KNS Group LLC (YADRO)
+#
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(perf)
+
+target_sources(app PRIVATE src/main.c)

samples/subsys/profiling/perf/README.rst

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+.. zephyr:code-sample:: profiling-perf
+   :name: Perf tool
+
+    Send perf samples to the host with console support
+
+This application can be used to demonstrate :ref:`profiling-perf` work.
+
+Requirements
+************
+
+Perf tool so far implemente only for riscv and x86_64 architectures.
+
+Usage example
+*************
+
+Build an image with:
+
+.. zephyr-app-commands::
+    :zephyr-app: samples/subsys/profiling/perf
+    :board: qemu_riscv64
+    :goals: build
+    :compact:
+
+After the sample starts, enter shell command:
+
+.. code-block:: console
+
+  uart:~$ perf record <period> <frequency>
+
+Wait for the completion message ``perf done!`` or ``perf buf override!``
+(if perf buffer size is smaller than required).
+
+Print made by perf samles in terminal by shell-command:
+
+.. code-block:: console
+
+  uart:~$ perf printbuf
+
+Output exaple:
+
+.. code-block:: console
+
+    Perf buf length 2046
+    0000000000000004
+    00000000001056b2
+    0000000000108192
+    000000000010052f
+    0000000000000000
+      ....
+    000000000010052f
+    0000000000000000
+
+Copy gotten output in some file, for example *perf_buf*.
+
+Make graph.svg with :zephyr_file:`scripts/perf/stackcollapse.py` and
+`FlameGraph`_:
+
+.. _FlameGraph: https://github.com/brendangregg/FlameGraph/
+
+.. code-block:: shell
+
+  python scripts/perf/stackcollapse.py perf_buf build/zephyr/zephyr.elf | <flamegraph_dir_path>/flamegraph.pl > graph.svg
+
+Graph example
+=============
+
+.. image:: images/graph_example.svg
+    :align: center
+    :alt: graph example