1908327 - Migrate finding in scope locations from Babel to lezer

Status: RESOLVED FIXED

(DevTools :: Debugger, task)

Description

[Alexandre Poirot [:ochameau]]

Babel parser (parser-worker.js) is by far the main performance culprit of the Debugger.

We do use the parser for various debugger frontend features, highlighted in the following document:
https://docs.google.com/document/d/12xq6Q5qDEuNDtKwSm9LwKSUA4k_zT-r96-3TWIimoqA/edit#heading=h.ldmzcj1wna5e

Thanks to the migration to CodeMirror 6 (bug 1773246), we will be able to use its new parser lezer.
This parser supports parsing only chunks of code and will allow us to only parse the current viewport.
Babel only supports parsing the whole file, which is the main reason why this particular part of the debugger is slow.

Comment 1

[Hubert Boma Manilla (:bomsy)]

Attachment: Bug 1908327 - [devtools] Migrate getting in scope locations from CM6 parser instead of the parser worker r=#devtools

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/6ca339ffce82
[devtools] Migrate getting in scope locations from CM6 parser instead of the parser worker r=devtools-reviewers,ochameau

Comment 3

[Norisz Fay [:noriszfay]]

Backed out for causing multiple dt failures

Backout link

Push with failures

Failure log

There are also failures with log parsing skipped like this one

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0e66b7737698
[devtools] Migrate getting in scope locations from CM6 parser instead of the parser worker r=devtools-reviewers,ochameau

Comment 5

[amarc]

Backed out for causing multiple dt failures

• Backout link
• Push with failures
• Failure Log
• Failure Log 2
• Failure Log 3
• Failure Log 4
• Failure Log 5
• Failure Log 6
• Failure Log 7

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c896521751db
[devtools] Migrate getting in scope locations from CM6 parser instead of the parser worker r=devtools-reviewers,ochameau

Comment 7

[amarc]

https://hg.mozilla.org/mozilla-central/rev/c896521751db

Comment 8

[Florin Bilt]

(In reply to Norisz Fay [:noriszfay] from comment #3)

Backed out for causing multiple dt failures

Backout link

Push with failures

Failure log

There are also failures with log parsing skipped like this one

Perfherder has detected a devtools performance change from push a9fff10eecc6201bd71902ca278a3da19765c942.

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
11%	damp custom.jsdebugger.open-large-minified-file.DAMP	linux1804-64-shippable-qr	e10s fission stylo webrender	63.40 -> 56.55

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests.

If you need the profiling jobs you can trigger them yourself from treeherder job view or ask a sheriff to do that for you.

You can run these tests on try with ./mach try perf --alert 43886

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