1859736 - Vec allocation time is too high in WGR::PathBuilder

Status: RESOLVED FIXED

(Core :: Graphics: Canvas2D, defect)

Description

[Jamie Nicol [:jnicol]]

GenerateQuantizedPath() shows up in profiles of Charts-chartjs: https://share.firefox.dev/48T9STP (and Perf-Dashboard too)

This is mostly caused by reallocs when push()ing items in to the points and types vectors, eg in curve_to(). Then much less significantly in get_path() calling Vec::into_boxed_slice() causes the vectors' storages to be realloced to the exact size.

If we allocate a single PathBuilder in DrawTargetWebgl::SharedContext and reset it between uses, whilst persisting the Vec storage, then we can effectively reduce this just to allocating the Boxed slices in PathBuilder::get_path()

Unfortunately this doesn't translate to a win in the test overall, as the improvements it leads to in the sync portions are undone by an increased wait in ClientWebGLContext::GetFrontBuffer() in the async step. See profile. Which is unfortunate, but this still seems worthwhile fixing anyway.

Comment 1

[Jamie Nicol [:jnicol]]

We could go even further and provide nsTArray/thin_vecs from the gecko side, only needing additional allocs/copies when there is a cache miss in PathCache::FindOrInsertEntry. But given this will need invasive API changes and the gains will be eaten up by the sync texture wait anyway, I don't think that's a good idea.

Comment 2

[Jamie Nicol [:jnicol]]

Attachment: Bug 1859736 - Update wpf-gpu-raster. r?#gfx-reviewers

DO NOT LAND: Change back to FirefoxGraphics repo after
https://github.com/FirefoxGraphics/wpf-gpu-raster/pull/2 has been
merged

Comment 3

[Jamie Nicol [:jnicol]]

Attachment: Bug 1859736 - Reuse WGR::PathBuilder instance in DrawTargetWebgl. r?#gfx-reviewers

This avoids some expensive vector reallocations.

Depends on D191282

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/92dd9aca656c
Update wpf-gpu-raster. r=gfx-reviewers,lsalzman
https://hg.mozilla.org/integration/autoland/rev/da6a29fc726b
Reuse WGR::PathBuilder instance in DrawTargetWebgl. r=gfx-reviewers,lsalzman
https://hg.mozilla.org/integration/autoland/rev/baf6a4468415
apply code formatting via Lando

Comment 5

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/92dd9aca656c
https://hg.mozilla.org/mozilla-central/rev/da6a29fc726b
https://hg.mozilla.org/mozilla-central/rev/baf6a4468415