Initial write-up of performance best practices and diagnostics. #231

DanielRosenwasser · 2019-10-08T17:31:56Z

At this point this is incomplete, but I'm looking for some feedback.

The current TODOs are

a section on taking TSServer traces
every  comment within the markdown
linking back to different pages (e.g. about project references and the like)

Things that I want feedback on

page title and location (where do users find this?)
what topics are we missing?
what topics are superfluous?
is the order correct? (e.g. should project structure come before discussion around project references?)

amcasey · 2019-10-08T17:43:59Z

https://github.com/Microsoft/JSTSdocs/blob/master/articles/troubleshooting/index.md#enable-detailed-language-service-logging

amcasey · 2019-10-08T17:51:47Z

My investigations so far have led me to believe that editor and batch slowness are investigated in completely different ways. Editor steps are largely written up at the link above (but could probably use some extra notes for VS Code users) and batch steps are still being developed.

Performance.md

johnnyreilly · 2019-10-08T18:07:24Z

Performance.md

+The `--incremental` flag allows TypeScript to save state from the last compilation to a `.tsbuildinfo` file.
+This file is used to figure out the smallest set of files that might to be re-checked/re-emitted since it last ran, much like how TypeScript's `--watch` mode works.
+
+Incremental compiles are enabled by default when using the `composite` flag for project references, but can bring the same speed-ups for any project that opts in.


One thing I realized subsequent to writing this post:

https://blog.johnnyreilly.com/2019/09/start-me-up-ts-loader-meet-tsbuildinfo.html

Is that .tsbuildinfo is only emitted in a projectReferences setup. That was surprising to me and to a bunch of others that commented on various ts-loader issues after the fact.

I don't know if it will ever be available standalone? Either way, good that the knowledge is captured here 😀

From looking at the commits it sounds like as of recently it's emitted, but only in --watch mode. (but maybe @sheetalkamat and @andrewbranch can clarify).

Sorry, I don't understand the question. I'm pretty sure --watch works on non-composite projects, so I'm not sure what "standalone" means. Maybe there's no API exposing it?

Performance.md

amcasey

Initial thoughts.

amcasey · 2019-10-19T00:43:46Z

Performance.md

+
+You can read up more about project references here. <!-- TODO -->
+
+# Configuring `tsconfig.json`


Some notes on jsconfig: https://github.com/microsoft/JSTSdocs/blob/a00dba5654676b16c97a4c1f1331fd1915b44019/articles/configuration/tsconfig.md#configuring-javascript-using-a-jsconfigjson-file

Performance.md

amcasey · 2019-10-19T00:52:10Z

Performance.md

+TypeScript compilation is often performed with other build tools in mind - especially when writing web apps that might involve a bundler.
+While we can only make suggestions for a few build tools, ideally these techniques can be generalized.
+
+## Concurrent Type-Checking


I'm not sure I understand the purpose of this paragraph.

If you have slow type-checks that impact watch mode, you you might benefit from running type-checking concurrently.

So the scenario is that you're using watch mode to keep your output directory up-to-date, rather than to find errors in your code? And this paragraph says you can have both using a plugin?

amcasey · 2019-10-19T00:53:31Z

Performance.md

+
+There are certain ways to get hints of what might be going wrong.
+
+## `extendedDiagnostics`


Obviously, this doesn't apply when the problem is editor responsiveness.

Why wouldn't it? Knowing that program construction time is the bottleneck might be a nice early hint.

Well, the most obvious reason would be that you can't just tack --extendedDiagnostics onto an existing command line - you have to figure out how to invoke tsc for your project and then add the switch. It would also help to know which of these line items apply only to tsc.

Normally when investigating performance I quickly glace at the tsserver log to see there aren't any too frequent DirectoryWatcher's invocations that are causing these (in that case its a configuration issue or a bug) otherwise I do run tsc --extendedDiagnostics to see whats going on... In these cases its either checkTime that is bottleneck or Program Time if there are too many modules and resolution taking longer.. That's what gives me hint on what to check next.

amcasey · 2019-10-19T00:56:14Z

Performance.md

+It's not always obvious what settings a compilation is being run with when running `tsc`, especially given that `tsconfig.json`s can extend other configuration files.
+`showConfig` can explain what `tsc` will calculate for an invocation.
+
+```sh


Note that the output will look like a tsconfig file but can't necessarily be used as one, since it may include command-line only options.

amcasey · 2019-10-19T00:57:33Z

Performance.md

+
+## `traceResolution`
+
+Running with `traceResolution` can help explain *why* a file was included in a compilation.


Is the resulting file actionable?

amcasey · 2019-10-19T00:58:12Z

Performance.md

+
+Some questions to keep in mind:
+
+* Is there a major difference in build times between `tsc` and the build tool with TypeScript integration?


Note that --extendedDiagnostics does not report the elapsed time, esp if there are multiple projects.

What's that "especially" hint at?

AFAIK, it prints per-project totals but not a cumulative total (or any of the overhead involved in ordering the projects for building).

Performance.md

DanielRosenwasser · 2019-10-29T17:52:16Z

Gonna try to get instructions in for TSServer traces in VS later on.

Initial write-up of performance best practices.

8065c7d

DanielRosenwasser requested review from gcrev93, RyanCavanaugh, sheetalkamat and amcasey October 8, 2019 17:31

johnnyreilly reviewed Oct 8, 2019

View reviewed changes

Addressed feedback and added tracing section.

50230a6

amcasey reviewed Oct 19, 2019

View reviewed changes

sheetalkamat reviewed Oct 23, 2019

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DanielRosenwasser added 2 commits October 29, 2019 10:49

Updates.

8aa202c

Link to project references.

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DanielRosenwasser merged commit adb1638 into master Oct 29, 2019

DanielRosenwasser deleted the perf branch October 29, 2019 17:52

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Initial write-up of performance best practices and diagnostics. #231

Initial write-up of performance best practices and diagnostics. #231

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DanielRosenwasser commented Oct 29, 2019


		You can read up more about project references here. <!-- TODO -->

		# Configuring `tsconfig.json`


		There are certain ways to get hints of what might be going wrong.

		## `extendedDiagnostics`


		## `traceResolution`

		Running with `traceResolution` can help explain why a file was included in a compilation.


		Some questions to keep in mind:

		* Is there a major difference in build times between `tsc` and the build tool with TypeScript integration?

Initial write-up of performance best practices and diagnostics. #231

Initial write-up of performance best practices and diagnostics. #231

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DanielRosenwasser commented Oct 29, 2019

DanielRosenwasser commented Oct 8, 2019 •

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