From 1c644797eb81a01e7b1a16eebc35e143dd74cff3 Mon Sep 17 00:00:00 2001 From: RafaelGSS Date: Thu, 10 Nov 2022 00:02:54 -0300 Subject: [PATCH] doc: include poor-performance diagnostic --- locale/en/docs/guides/diagnostics/index.md | 1 + .../diagnostics/poor-performance/index.md | 36 ++++++++ .../poor-performance/using-linux-perf.md | 87 +++++++++++++++++++ 3 files changed, 124 insertions(+) create mode 100644 locale/en/docs/guides/diagnostics/poor-performance/index.md create mode 100644 locale/en/docs/guides/diagnostics/poor-performance/using-linux-perf.md diff --git a/locale/en/docs/guides/diagnostics/index.md b/locale/en/docs/guides/diagnostics/index.md index 9ef6d6b48f278..176b089239a6c 100644 --- a/locale/en/docs/guides/diagnostics/index.md +++ b/locale/en/docs/guides/diagnostics/index.md @@ -17,5 +17,6 @@ This is the available set of diagnostics guides: * [Memory](/en/docs/guides/diagnostics/memory) * [Live Debugging](/en/docs/guides/diagnostics/live-debugging) +* [Poor Performance](/en/docs/guides/diagnostics/poor-performance) [Diagnostics Working Group]: https://github.com/nodejs/diagnostics diff --git a/locale/en/docs/guides/diagnostics/poor-performance/index.md b/locale/en/docs/guides/diagnostics/poor-performance/index.md new file mode 100644 index 0000000000000..769c690f8dbd9 --- /dev/null +++ b/locale/en/docs/guides/diagnostics/poor-performance/index.md @@ -0,0 +1,36 @@ +--- +title: Poor Performance - Diagnostics +layout: docs.hbs +--- + +# Poor Performance + +In this document you can learn about how to profile a Node.js process. + +* [Poor Performance](#poor-performance) + * [My application has a poor performance](#my-application-has-a-poor-performance) + * [Symptoms](#symptoms) + * [Debugging](#debugging) + +## My application has a poor performance + +### Symptoms + +My applications latency is high and I have already confirmed that the bottleneck +is not my dependencies like databases and downstream services. So I suspect that +my application spends significant time to run code or process information. + +You are satisfied with your application performance in general but would like to +understand which part of our application can be improved to run faster or more +efficient. It can be useful when we want to improve the user experience or save +computation cost. + +### Debugging + +In this use-case, we are interested in code pieces that use more CPU cycles than +the others. When we do this locally, we usually try to optimize our code. + +This document provides two simple ways to profile a Node.js application: + +* [Using V8 Sampling Profiler](https://nodejs.org/en/docs/guides/simple-profiling/) +* [Using Linux Perf](/en/docs/guides/diagnostics/poor-performance/using-linux-perf) diff --git a/locale/en/docs/guides/diagnostics/poor-performance/using-linux-perf.md b/locale/en/docs/guides/diagnostics/poor-performance/using-linux-perf.md new file mode 100644 index 0000000000000..ff583752efd8d --- /dev/null +++ b/locale/en/docs/guides/diagnostics/poor-performance/using-linux-perf.md @@ -0,0 +1,87 @@ +--- +title: Poor Performance - Using Linux Perf +layout: docs.hbs +--- + +# Using Linux Perf + +[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 + +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 a Node.js 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: [linux-perf](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. + +```console +# 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: + +```console +$ 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. + +To aggregate those results in a specific file execute: + +```console +$ sudo perf script > perfs.out +``` + +```console +$ 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]) +.... +``` + +The raw output can be a bit hard to understand so typically the raw file is used 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. + +Because `perf` output is not a Node.js 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://www.brendangregg.com/blog/2014-09-17/node-flame-graphs-on-linux.html +* https://perf.wiki.kernel.org/index.php/Main_Page +* https://blog.rafaelgss.com.br/node-cpu-profiler