1854423 - Optimize the getColumnBreakpoints selector

Status: RESOLVED FIXED

(DevTools :: Debugger, enhancement)

Description

[Alexandre Poirot [:ochameau]]

Here is a record of bug 1843454 STR:
https://share.firefox.dev/3Lwgcqi
On this 50s record, we spend 1.5s in getColumnBreakpoints selector:
https://searchfox.org/mozilla-central/rev/077fc34d03b85b09add26b5f99f1a3a3a72c8720/devtools/client/debugger/src/selectors/visibleColumnBreakpoints.js#124-151
This probably causes some junks as it happens in the main thread.

Following this str, we do manipulate an array with 260k elements.
Quickly looking at its implementation, there is lots of room for improvement.

Comment 1

[Alexandre Poirot [:ochameau]]

Attachment: Bug 1854423 - [devtools] Stop querying isOriginalId from getSelectedLocation.

Checking for isOriginal boolean is much faster as it avoid a string comparison and function calls.

Comment 2

[Alexandre Poirot [:ochameau]]

Attachment: Bug 1854423 - [devtools] Optimize and simplify getVisibleColumnBreakpoint selector.

• filterByLineCount was just a very costly non-sense filtering nothing.
  (comes from unreviewed code https://github.com/firefox-devtools/debugger/pull/7349)
• The filter using lineText isn't clear either.
  Why would breakpoint position include breakpoint after the end of the actual line text content??

Comment 3

[Alexandre Poirot [:ochameau]]

With the attached patch, I get down to less than 180ms spent in this selector.
https://share.firefox.dev/48r2z5K

Comment 4

[Alexandre Poirot [:ochameau]]

Expected improvements:
https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=43c06a822362f1cdcbd63b074ccabc96f4e85fd6&originalSignature=4763542&newSignature=4763542&framework=12&application=firefox&originalRevision=85c14852074270cef008ebc7fce3187d5dd4c22e&page=1&showOnlyConfident=1

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/409956a5ade5
[devtools] Stop querying isOriginalId from getSelectedLocation. r=nchevobbe,devtools-reviewers
https://hg.mozilla.org/integration/autoland/rev/9feea518d33a
[devtools] Optimize and simplify getVisibleColumnBreakpoint selector. r=devtools-reviewers,bomsy

Comment 6

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/409956a5ade5
https://hg.mozilla.org/mozilla-central/rev/9feea518d33a

Comment 7

[Julian Descottes [:jdescottes]]

== Change summary for alert #39943 (as of Thu, 12 Oct 2023 20:34:05 GMT) ==

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
5%	damp custom.jsdebugger.stepIn.DAMP	linux1804-64-shippable-qr	e10s fission stylo webrender-sw	567.13 -> 539.64
4%	damp custom.jsdebugger.pretty-print.reload-and-pause.DAMP	macosx1015-64-shippable-qr	e10s fission stylo webrender	8,510.49 -> 8,211.90
3%	damp custom.jsdebugger.stepInNewSource.DAMP	windows10-64-shippable-qr	e10s fission stylo webrender	569.72 -> 552.27
3%	damp custom.jsdebugger.pretty-print.reload-and-pause.DAMP	macosx1015-64-shippable-qr	e10s fission stylo webrender-sw	8,460.01 -> 8,206.87
3%	damp custom.pretty-print.jsdebugger.reload.DAMP	macosx1015-64-shippable-qr	e10s fission stylo webrender	8,304.10 -> 8,059.49
2%	damp custom.jsdebugger.pretty-print.reload-and-pause.DAMP	windows10-64-shippable-qr	e10s fission stylo webrender	8,308.96 -> 8,108.50

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=39943