1933787 - Implement object previews/grips in C++

Status: RESOLVED FIXED

(DevTools :: Debugger, enhancement, P3)

Description

[Alex Thayer [:alexical] (she/her)]

Basically, creating previews for objects is rather expensive, and can be made much faster if implemented in C++. Simply migrating the existing JS logic into C++ is a significant speedup, but there's also more work we can do by serializing the preview into a binary representation which can be more efficiently passed to the parent process and included in profiles / elsewhere. This bug tracks at least the first part of this, and it may be most expedient to just do the serialization work as part of this.

Comment 1

[Alex Thayer [:alexical] (she/her)]

Attachment: WIP: Bug 1933787 - Object Previews in C++

Comment 2

[Alex Thayer [:alexical] (she/her)]

Attachment: Bug 1933787 - Record arg values in tracer-generated profiles r?arai

Comment 3

[Alexandre Poirot [:ochameau]]

The lastest mozilla-central patch can be tested by settting devtools.performance.recording.ui-base-url to https://deploy-preview-5363--perf-html.netlify.app/.
Doing this help use a custom profiler frontend that supports showing arg values, which comes from the following pull request:
https://github.com/firefox-devtools/profiler/pull/5363

With such setup, you can record traces that look like this:
https://deploy-preview-5363--perf-html.netlify.app/public/rxabzrr1e4fcb8f05aavnbm7vsgcp4cn2hg7mtr/stack-chart/?globalTrackOrder=a0w9&hiddenGlobalTracks=1w8&hiddenLocalTracksByPid=4612-0w4~4636-0~4617-0&thread=f&timelineType=category&v=10
See the popups when mouse overing the frames in the stack chart.

Comment 4

[Nicolas Chevobbe [:nchevobbe]]

Attachment: args grip in the profiler stackframe tab

Adding a screenshot for posterity

This looks very promising :)

(Looks like the profiler might need to handle overflowing in the tooltip)

Comment 5

[Fatih Kilic [:fkilic]]

I just tried it, pretty cool. One question, will we be able to see arguments (and possibly return values) into native calls? Like not only to functions, but to CanvasRenderingContext2D.fillText for example

Comment 6

[Alexandre Poirot [:ochameau]]

Attachment: reps rendering of dom element

I crafted a WIP patch on top of :alexical's one against the profiler frontend in order to show the previews via DevTools Reps (React component used by the console to render any arbitraty JS value nicely):
https://github.com/firefox-devtools/profiler/pull/5394
(More info on github about the challenges of integrating reps into the profiler frontend)

Using the same mozilla-central patch attached on this bug: https://phabricator.services.mozilla.com/D236936
and then setting devtools.performance.recording.ui-base-url to https://deploy-preview-5394--perf-html.netlify.app/,
you should be able to see tracer values like on this profiler record:
https://deploy-preview-5394--perf-html.netlify.app/public/rxabzrr1e4fcb8f05aavnbm7vsgcp4cn2hg7mtr/stack-chart/?globalTrackOrder=a0w9&hiddenGlobalTracks=1w8&hiddenLocalTracksByPid=4612-0w4~4636-0~4617-0&implementation=js&search=activity-s&thread=f&timelineType=category&v=10

Comment 7

[Alex Thayer [:alexical] (she/her)]

Attachment: Bug 1933787 - Record basic DOM types in execution tracer r?arai

Comment 8

[Alex Thayer [:alexical] (she/her)]

Attachment: Bug 1933787 - Ingest traced values from profiler backend r?canaltinova

Comment 9

[Alex Thayer [:alexical] (she/her)]

Quick update on this: work still ongoing, but I should have a big update to the followup patches for DOM types and the profiler integration later today, together with an integration test that tests both the JS and DOM side of things.

Comment 10

[Alex Thayer [:alexical] (she/her)]

Attachment: Bug 1933787 - Test traced values with JSObjectsTestUtils r?ochameau

This does not represent the finalized form for a lot of the entries in the
snapshot since some types are still not handled, but this at least lets us
exercise the code paths and ensure future additions don't change the
representations of any existing covered types. I would also like to move
the serialization code here into a module we can include from Firefox and
the profiler frontend but that's for a future patch.

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/9ae82fa7ca01
https://hg.mozilla.org/integration/autoland/rev/84a3f04d24c9
Record arg values in tracer-generated profiles r=arai
https://github.com/mozilla-firefox/firefox/commit/b44d3787446c
https://hg.mozilla.org/integration/autoland/rev/0bf7cd7f1433
Record basic DOM types in execution tracer r=arai
https://github.com/mozilla-firefox/firefox/commit/7d647fcc3916
https://hg.mozilla.org/integration/autoland/rev/bc9aaa1e5493
Ingest traced values from profiler backend r=profiler-reviewers,canaltinova
https://github.com/mozilla-firefox/firefox/commit/3f4b38cf9912
https://hg.mozilla.org/integration/autoland/rev/177ef66cab89
Test traced values with JSObjectsTestUtils r=ochameau,devtools-reviewers,profiler-reviewers,canaltinova

Comment 12

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/dc4ef273dd82
https://hg.mozilla.org/integration/autoland/rev/ab1f4f1be64d
Revert "Bug 1933787 - Test traced values with JSObjectsTestUtils r=ochameau,devtools-reviewers,profiler-reviewers,canaltinova" for causing build bustages @ ExecutionTracer.h

Comment 13

[Sandor Molnar[:smolnar]]

Backed out for causing build bustages @ ExecutionTracer.h

Backout link: https://hg.mozilla.org/integration/autoland/rev/ab1f4f1be64dbebcb4fee3868a4ff130ee397965

Push with failures

Failure log -> /builds/worker/checkouts/gecko/js/src/debugger/ExecutionTracer.h:236:26: error: variable 'encodingBits' set but not used [-Werror=unused-but-set-variable]

Comment 14

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/6d7cb1b94f33
https://hg.mozilla.org/integration/autoland/rev/e38e3daf1fcc
Record arg values in tracer-generated profiles r=arai
https://github.com/mozilla-firefox/firefox/commit/af8ea6fa72dd
https://hg.mozilla.org/integration/autoland/rev/14e2947f2bb5
Record basic DOM types in execution tracer r=arai
https://github.com/mozilla-firefox/firefox/commit/dba048f0e494
https://hg.mozilla.org/integration/autoland/rev/3496f5b12f3b
Ingest traced values from profiler backend r=profiler-reviewers,canaltinova
https://github.com/mozilla-firefox/firefox/commit/7d5d0d0cd2a3
https://hg.mozilla.org/integration/autoland/rev/c820ceb3fda4
Test traced values with JSObjectsTestUtils r=ochameau,devtools-reviewers,profiler-reviewers,canaltinova

Comment 15

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/d0928a3847b5
https://hg.mozilla.org/integration/autoland/rev/22eb2254b7a9
Revert "Bug 1933787 - Test traced values with JSObjectsTestUtils r=ochameau,devtools-reviewers,profiler-reviewers,canaltinova" for causing failures at test_feature_java.js.

Comment 16

[Atila Butkovits]

Backed out for causing failures at test_feature_java.js

Backout link: https://hg-edge.mozilla.org/integration/autoland/rev/22eb2254b7a90581851991892a7e870156aed4ed

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=c820ceb3fda4f0e6d8a05a34431f451c717ef610&selectedTaskRun=eT4g4EU4Rr2a6rENOjMR8w.0

Failure log: https://treeherder.mozilla.org/logviewer?job_id=518798628&repo=autoland&lineNumber=1817

Comment 17

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/21a2b5afec93
https://hg.mozilla.org/integration/autoland/rev/5f32c9dda3cd
Record arg values in tracer-generated profiles r=arai
https://github.com/mozilla-firefox/firefox/commit/b1c7a723c1df
https://hg.mozilla.org/integration/autoland/rev/b8d87d0224c2
Record basic DOM types in execution tracer r=arai
https://github.com/mozilla-firefox/firefox/commit/47fe67ebb3e1
https://hg.mozilla.org/integration/autoland/rev/b4948b0d58b3
Ingest traced values from profiler backend r=profiler-reviewers,canaltinova
https://github.com/mozilla-firefox/firefox/commit/b3f9f9a50ec8
https://hg.mozilla.org/integration/autoland/rev/0c7eeec56eab
Test traced values with JSObjectsTestUtils r=ochameau,devtools-reviewers,profiler-reviewers,canaltinova

Comment 18

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/5f32c9dda3cd
https://hg.mozilla.org/mozilla-central/rev/b8d87d0224c2
https://hg.mozilla.org/mozilla-central/rev/b4948b0d58b3
https://hg.mozilla.org/mozilla-central/rev/0c7eeec56eab