77948 - Improve ReflowInput's constructor

Status: REOPENED

(Core :: Layout, defect, P5)

Description

[Chris Waterson]

nsHTMLReflowState's ctor is fairly expensive considering how often it's called;
we should examine it to determine if there are ways it can be improved. For
example, could we compute some of the information lazily? (I know of at least
one case where the state is constructed, but only one field is actually used.)

Anyway, this shows up on profiles of long pages. Filing a bug so the task can be
tracked.

Comment 1

[Brian Ryner (not reading)]

I can take this one.

Comment 2

[Brian Ryner (not reading)]

not going to make 0.9.6, will investigate for 0.9.7.

Comment 3

[Brian Ryner (not reading)]

will finish investigating this for 0.9.8.

Comment 4

[Brian Ryner (not reading)]

Back over to you, waterson... I'm not going to have time to get to this.  Maybe
we can pass it around to someone else if it turns out to be important.

Comment 5

[Randell Jesup [:jesup] (needinfo me)]

Comments from bug 116437, which is about a 24MB file taking forever to layout.
The jprof is at http://bugzilla.mozilla.org/showattachment.cgi?attach_id=65191
Shows 3% in nsReflowState::nsReflowState()

Typical: 
  Mostly Reflowing lines:

12% direct (90% total) in ReflowDirtyLines()
4% total in nsFontCache::GetMetricsFor()
6% direct in nsBlockReflowState::RecoverStateFrom()
2% direct in nsBlockFrame::PropagateFloaterDamage()
3% total in nsFrame::Invalidate()
10% direct in nsLineBox::GetCombinedArea()
4% direct, 13% total in nsBlockFrame::ComputeFinalSize()
6% direct in nsBlockFrame::BuildFloaterList()
8% total in nsBlockFrame::PlaceLine()
1.5% total in nsCSSRendering::FindBackground
3% total in nsHTMLReflowState::nsHTMLReflowState
5% direct in nsFrameList::LastChild
10% total in nsRenderingContextGTK::GetTextDimensions()

Comment 6

[Marek Z. Jeziorek]

batch: adding topembed per Gecko2 document
http://rocknroll.mcom.com/users/marek/publish/Gecko/Gecko2Tasks.html

Comment 7

[Jaime Rodriguez, Jr.]

--> for reassignment. 

Changing from topembed, to embed, as this is not currently blocking a major
embedding customer.

Comment 8

[Michael Buckland]

Bulk adding topembed keyword.  Gecko/embedding needed.

Comment 9

[Kevin McCluskey (gone)]

nsbeta1-

Comment 10

[Sylvestre Ledru [:Sylvestre]]

Time to close it.

Comment 11

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

I think this is still an issue.

Comment 12

[BugBot [:suhaib / :marco/ :calixte]]

The meta keyword is there, the bug doesn't depend on other bugs and there is no activity for 12 months.
:svoisen, maybe it's time to close this bug?

Comment 13

[Sean Voisen (:svoisen)]

Removing meta to get off mgmt bot's list.

Comment 14

[Ting-Yu Lin [:TYLin] (PDT, UTC-7)]

Change the bug title because nsHTMLReflowState has been renamed to ReflowInput in bug 1277129.

One example jumps into my mind, which might worth improving, is
https://searchfox.org/mozilla-central/rev/9e45d74b956be046e5021a746b0c8912f1c27318/layout/generic/nsBlockFrame.cpp#3528-3536