1363423 - Extremely bad PresShell::Paint performance on http://a816-dohbesp.nyc.gov/IndicatorPublic/dognames/

Status: RESOLVED FIXED

(Core :: Panning and Zooming, defect, P2)

Description

[Mike Conley (:mconley) (:⚙️) (PTO: May 24 - June 2nd)]

STR (warning - will kill main thread):

1. Visit http://a816-dohbesp.nyc.gov/IndicatorPublic/dognames/


This absolutely kills the main thread. Here's a profile I captured:

https://perfht.ml/2qOkBNl

It seems like we're spending a lot of time in PresShell::Paint. Like, multiple seconds.

Hey jrmuizel, anything useful in here? Is this a known bug?

Comment 1

[Jeff Muizelaar [:jrmuizel]]

Nice. AccumulateEventRegions is the culprit. We should investigate why the event region is so large.

Comment 2

[Botond Ballo [:botond]]

Yikes. We're building a maybe-hit region with 1.26 million rectangles! We probably shouldn't be doing that :)

Comment 3

[Botond Ballo [:botond]]

This is very similar to bug 1333195. In that testcase, the maybe-hit region "only" has about 190,000 rects.

Comment 4

[Botond Ballo [:botond]]

We previously added a |mMaybeHitRegion.SimplifyOutward(8)| call to AccumulateEventRegions() in bug 1200158, but then removed it in bug 1201548.

I don't see a correctness reason for removing it in bug 1201548, we just no longer needed it to address a different performance problem, so I think it should be safe to put back.

Comment 5

[Botond Ballo [:botond]]

Attachment: Bug 1363423 - Prevent the maybe-hit region from growing too large (in terms of number of rectangles) in PaintedLayerData::AccumulateEventRegions().

Review commit: https://reviewboard.mozilla.org/r/139022/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/139022/

Comment 6

[Botond Ballo [:botond]]

(I also invesigated using TiledRegion instead, but I didn't see any performance wins compared to SimplifyOutward, and it's more complicated code-wise, so we're going to stick with the SimplifyOutward approach.)

Comment 8

[Jeff Muizelaar [:jrmuizel]]

Comment on attachment 8867483 [details]
Bug 1363423 - Prevent the maybe-hit region from growing too large (in terms of number of rectangles) in PaintedLayerData::AccumulateEventRegions().

https://reviewboard.mozilla.org/r/139022/#review143656

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c5ac37367e2e
Prevent the maybe-hit region from growing too large (in terms of number of rectangles) in PaintedLayerData::AccumulateEventRegions(). r=jrmuizel

Comment 10

[Iris Hsiao [:ihsiao]]

https://hg.mozilla.org/mozilla-central/rev/c5ac37367e2e