748512 - Investigate slowness when switching scripts while debugging

Status: RESOLVED FIXED

(DevTools :: Debugger, defect, P3)

Description

[Rob Campbell [:rc] (:robcee)]

Start the Debugger on a page with a lot of scripts. There may be some startup slowness populating the list of scripts.

Comment 1

[Rob Campbell [:rc] (:robcee)]

Good example case is twitter.com. Switching scripts with the list is quite slow.

Comment 2

[Victor Porof [:vporof][:vp]]

I herd some orion updates will autofix this.

Comment 3

[Rob Campbell [:rc] (:robcee)]

from playing with this in the SPS profiler, the following stand out:

_modifyContent > _updatePage > _createLine 20.9% > _createSpan 9.9%

… _getLineBoundingClientRect 12.1% >DoReflow 11%


_modifyContent and updatePage seem to be pretty heavy hitters, consuming a high percentage of time. They reduce to _createLine and _createSpan being the big culprits in there. I think some targetted profiling around these methods would help.

_getLineBoundingClientRect is another big contender causing reflows with every invocation.

Comment 4

[Victor Porof [:vporof][:vp]]

(In reply to Rob Campbell [:rc] (:robcee) from comment #3)
> from playing with this in the SPS profiler, the following stand out:
> 
> _modifyContent > _updatePage > _createLine 20.9% > _createSpan 9.9%
> 
> … _getLineBoundingClientRect 12.1% >DoReflow 11%
> 
> 
> _modifyContent and updatePage seem to be pretty heavy hitters, consuming a
> high percentage of time. They reduce to _createLine and _createSpan being
> the big culprits in there. I think some targetted profiling around these
> methods would help.
> 
> _getLineBoundingClientRect is another big contender causing reflows with
> every invocation.

Awesome profiling is awesome. I guess these are all methods implemented in the orion engine. Maybe showing these results to the orion people would help them?

Comment 5

[Mihai Sucan [:msucan]]

(In reply to Victor Porof [:vp] from comment #4)
> Awesome profiling is awesome. I guess these are all methods implemented in
> the orion engine. Maybe showing these results to the orion people would help
> them?

Indeed. I'm already on it - contacted them. Upstream is aware of the issues, but we haven't come yet to a solution to avoid the numerous calls to "reflow triggers".

Thanks Rob for profiling!

Comment 6

[Victor Porof [:vporof][:vp]]

Let's check on this again after Orion is updated.

Comment 7

[Eddy Bruel [:ejpbruel]]

Victor, any update on this?

Comment 8

[Victor Porof [:vporof][:vp]]

Nobody is working on this, but I haven't heard any complains after our switch to CodeMirror.

Comment 9

[Eddy Bruel [:ejpbruel]]

(In reply to Victor Porof [:vporof][:vp] from comment #8)
> Nobody is working on this, but I haven't heard any complains after our
> switch to CodeMirror.

Should be safe to close this bug then. We can always reopen when it becomes a problem again in the future.