1435649 - Don't touch the display item when taking the early return in ComputeGeometryChangeForItemW

Status: RESOLVED FIXED

(Core :: Web Painting, enhancement, P3)

Description

[Matt Woodrow (:mattwoodrow)]

Attachment: reused-on-did

We try to take an early return in ComputeGeometryChangeForItem when the item wasn't rebuilt by retained-dl, but unfortunately this still dereferences the item and takes almost as long as the full invalidation code.

We can store the value on the DisplayItemData earlier (when the item is already in cache), and avoid needing to touch it here.

Comment 1

[Jamie Nicol [:jnicol]]

Comment on attachment 8948297 [details] [diff] [review]
reused-on-did

Review of attachment 8948297 [details] [diff] [review]:
-----------------------------------------------------------------

Looks good, just a question and a nit.

::: layout/painting/FrameLayerBuilder.cpp
@@ +185,5 @@
>  void
>  DisplayItemData::EndUpdate()
>  {
>    MOZ_RELEASE_ASSERT(mLayer);
> +  mItem = nullptr;

Why does the assertion no longer hold?

::: layout/painting/FrameLayerBuilder.h
@@ +184,5 @@
>      * paint) has been updated in the current paint.
>      */
>    bool            mUsed;
>    bool            mIsInvalid;
> +  bool            mReusedItem;

Can we call this mIsReusedItem, or something indicating it's a bool?

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/4aa9b74724b8
Don't deference the display item when attempting the early return in ComputeGeometryChangeForItem to avoid a cache miss. r=jnicol

Comment 3

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/4aa9b74724b8

Comment 4

[Ionuț Goldan [:igoldan]]

These performance improvements landed thanks to this bug and bug 1435650!

== Change summary for alert #11512 (as of Mon, 12 Feb 2018 04:03:33 GMT) ==

Improvements:

 12%  displaylist_mutate osx-10-10 opt e10s stylo     7,425.25 -> 6,561.79
  8%  displaylist_mutate linux64 opt e10s stylo       2,998.83 -> 2,763.43
  8%  displaylist_mutate linux64 pgo e10s stylo       2,565.03 -> 2,367.67
  8%  displaylist_mutate windows7-32 pgo e10s stylo   5,145.52 -> 4,750.92
  7%  displaylist_mutate windows10-64 pgo e10s stylo  4,819.58 -> 4,464.75

For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=11512