1435650 - Avoid calling GetOffsetToCrossDoc during ProcessDisplayItems

Status: RESOLVED FIXED

(Core :: Web Painting, enhancement, P3)

Description

[Matt Woodrow (:mattwoodrow)]

Attachment: cache-agr-offset

We currently call GetOffsetToCrossDoc for every item, which dereferences the nsIFrame, and pulls it into the cache.

This is pretty bad, since processing most items shouldn't require this, and we spend a lot of time waiting for cache misses.

Generally, the AGR for each item will be the same as last time, so we can just cache the offset and only look it up when it changes.

We could also figure this out in advance and store an offset on each AGR itself, but that's more work, and I'm not sure it's worth it yet.

Comment 1

[Jamie Nicol [:jnicol] (PTO until 25th May)]

Comment on attachment 8948298 [details] [diff] [review]
cache-agr-offset

Review of attachment 8948298 [details] [diff] [review]:
-----------------------------------------------------------------

This looks good. Except I can't see what's happened to the old lastAnimatedGeometryRoot and lastAGRTopLeft variables, which were used in the mFlattenToSingleLayer code path. Won't that be affected?

Comment 2

[Matt Woodrow (:mattwoodrow)]

Sorry, forgot to add bug 1435643 as a dependency. I'm trying to get rid of the mFlattenToSingleLayer code path, so this patch doesn't need to worry about it.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/f840f8d4b7b1
Cache the offset from AGR to reference frame in ProcessDisplayItems. r=jnicol

Comment 4

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

https://hg.mozilla.org/mozilla-central/rev/f840f8d4b7b1