docs(linux-perf): add tutorial of linux_perf

documentation/profiling/step2/using_linux_perf.md

@@ -1,13 +1,72 @@
 # Using Linux Perf
 
-Linux Perf provides low level CPU profiling with JavaScript, native and OS level frames.
+[Linux Perf](https://perf.wiki.kernel.org/index.php/Main_Page) provides low level CPU profiling with JavaScript, native and OS level frames.
+
+**Important**: this tutorial is only available on Linux.
 
 ## How To
 
-// TODO
+Linux Perf is usually available through the `linux-tools-common` package. Through either `--perf-basic-prof` or `--perf-basic-prof-only-functions` we are able to start an nodejs application supporting _perf_events_.
+
+> `--perf-basic-prof` will always write to a file (/tmp/perf-PID.map), which can lead to infinite disk growth. If that’s a concern either use the module: https://www.npmjs.com/package/linux-perf or `--perf-basic-prof-only-functions`
+
+The main difference between both is that `--perf-basic-prof-only-functions` produces less output, it is a viable option for production profiling.
+
+```sh
+# Launch the application an get the PID
+node --perf-basic-prof-only-functions index.js &
+[1] 3870
+```
+
+Then record events based in the desired frequency:
+
+```sh
+sudo perf record -F 99 -p 3870 -g
+```
+
+In this phase, you may want to use a load test in the application in order to generate more records for a reliable analysis. When the job is done, close the perf process by sending a SIGINT (Ctrl-C) to the command.
+
+The `perf` will generate a file inside the `/tmp` folder, usually called `/tmp/perf-PID.map`(in above example: `/tmp/perf-3870.map`) containing the traces for each function called.
+
+For aggregate those results in specific file execute:
+
+```sh
+sudo perf script > perfs.out
+```
+
+```sh
+cat ./perfs.out
+node 3870 25147.878454:          1 cycles:
+        ffffffffb5878b06 native_write_msr+0x6 ([kernel.kallsyms])
+        ffffffffb580d9d5 intel_tfa_pmu_enable_all+0x35 ([kernel.kallsyms])
+        ffffffffb5807ac8 x86_pmu_enable+0x118 ([kernel.kallsyms])
+        ffffffffb5a0a93d perf_pmu_enable.part.0+0xd ([kernel.kallsyms])
+        ffffffffb5a10c06 __perf_event_task_sched_in+0x186 ([kernel.kallsyms])
+        ffffffffb58d3e1d finish_task_switch+0xfd ([kernel.kallsyms])
+        ffffffffb62d46fb __sched_text_start+0x2eb ([kernel.kallsyms])
+        ffffffffb62d4b92 schedule+0x42 ([kernel.kallsyms])
+        ffffffffb62d87a9 schedule_hrtimeout_range_clock+0xf9 ([kernel.kallsyms])
+        ffffffffb62d87d3 schedule_hrtimeout_range+0x13 ([kernel.kallsyms])
+        ffffffffb5b35980 ep_poll+0x400 ([kernel.kallsyms])
+        ffffffffb5b35a88 do_epoll_wait+0xb8 ([kernel.kallsyms])
+        ffffffffb5b35abe __x64_sys_epoll_wait+0x1e ([kernel.kallsyms])
+        ffffffffb58044c7 do_syscall_64+0x57 ([kernel.kallsyms])
+        ffffffffb640008c entry_SYSCALL_64_after_hwframe+0x44 ([kernel.kallsyms])
+....
+```
+
+It's quite hard to get insights from this raw file and is a common sense to generate flamegraphs for a better visualization.
+
+
+![Example nodejs flamegraph](https://user-images.githubusercontent.com/26234614/129488674-8fc80fd5-549e-4a80-8ce2-2ba6be20f8e8.png)
+
+To generate a flamegraph from this result, follow [this tutorial](https://nodejs.org/en/docs/guides/diagnostics-flamegraph/#create-a-flame-graph-with-system-perf-tools) from step 6.
+
+Althought, `perf` output is not a node specific tool, it might have issues with how JavaScript code is optimized in Node.js. See [perf output issues](https://nodejs.org/en/docs/guides/diagnostics-flamegraph/#perf-output-issues) for a futher reference.
 
 ## Useful Links
 
-- https://nodejs.org/en/docs/guides/diagnostics-flamegraph/
+- https://nodejs.org/en/docs/guides/diagnostics-flamegraph/ (Further informations in how to generate the flamegraph)
 - [http://www.brendangregg.com/blog/2014-09-17/node-flame-graphs-on-linux.html](http://www.brendangregg.com/blog/2014-09-17/node-flame-graphs-on-linux.html)
-- https://github.com/mmarchini/node-linux-perf
+- https://perf.wiki.kernel.org/index.php/Main_Page
+- https://blog.rafaelgss.com.br/node-cpu-profiler