1424047 - ResolveFlattening is the hottest function during WR DisplayList building on facebook-refresh

Status: RESOLVED INVALID

(Core :: Graphics: WebRender, enhancement)

Description

[Jeff Muizelaar [:jrmuizel]]

https://perfht.ml/2nFUZ4T

mstange thinks we don't need to spend so much time here

Comment 1

[Jeff Muizelaar [:jrmuizel]]

Any thoughts Ethan?

Comment 2

[Ethan Lin[:ethlin]]

Attachment: Bug 1424047 - Use list to store the display item stack in FlattenedDisplayItemIterator.

Review commit: https://reviewboard.mozilla.org/r/206622/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/206622/

Comment 3

[Ethan Lin[:ethlin]]

The container of the stack seems to be the reason. I don't see the ResolveFlattening in the gecko profiler[1] after using std::list, though I'm not sure why the AutoTArray is slower in this case. Jeff, can you check if the patch helps? Maybe ClearInvalidationStateBits has the same problem. I'll investigate more deeply.

[1] https://perfht.ml/2Bihu60

Comment 4

[Jeff Muizelaar [:jrmuizel]]

So I looked at this more closely in Instruments. It turns out this is just the cache miss that we get for visiting the next nsDisplayItem.