Chrome Version       : 56.0.2914.3
OS Version: OS X 10.12.1

We want to examine the influence / overheads of layout when resizing a browser window.

What steps will reproduce the problem?
1. Open about:blank in Canary
2. Open activity monitor, sample
3. Quickly select the browser window and resize it aggresively

What is the expected result?

Buttery smooth resize

What happens instead of that?

Resize uses noticeable CPU and runs at <60 Hz.

Trace attached. Some highlights

Autolayout is present, but it's not a major contributor.
Significant overhead is in ObjC cruft and memory management.

2309 / 3000 samples has us "inside" a message loop (i.e not waiting for an event). Using that as 100% baseline.
2248 under handling of the mouse event for resize (i.e. most of it)

56% (1287/2309) is under [NSWindow _setFrame:updateBorderViewSize:]
36% (834/2309) of the time is latency (and a tiny bit of frame swap CPU time), under content::RenderWidgetHostImpl::PauseForPendingResizeOrRepaints()

20% remains: maybe half is autolayout, and the other half is other stuff we trigger (some probably avoidable):

There are many calls to ScreenMac::GetDisplayNearestWindow via various stacks. These calls are not cheap within AppKit (wait_for_user_home_dir?? get_bool_user_preference_for_key? SLDisplayUsesForceToGray? ICCProfile::FromCGColorSpace(CGColorSpace*)?)

1.6% in [AutocompleteTextField setFrame:]. About one third is autolayout.
 - a call to LocationBarViewMac::UpdateLocationIcon() which invokes NSImageFromImageSkiaWithColorSpace every time!?
  - and BubbleDecoration::SetImage, ChromeToolbarModelDelegate::GetSecurityLevel()

[NSView _postFrameChangeNotification] calls all over the place.
 ** -[BookmarkBarController reconfigureBookmarkBar] is one subscriber ** 2.5% of CPU time **
   - calls [NSView removeFromSuperview] and does lots of NSString rendering
   - [GradientButtonCell initTextCell:]
  ** Invoked again! via BackgroundGradientView setFrameSize, 


AutocompleteTextField addToolTip:

9+3 samples (0.5%) at -[NSView _verifyConstraintsForCurrentFrame] under [WebContentsViewCocoa setFrameSize:]
I only got 2 samples at -[NSView(NSConstraintBasedLayout) under RenderWidgetHostViewCocoa setFrameSize (i.e. <0.1%)


== 1022 / 2309 samples not in  [NSWindow _setFrame:updateBorderViewSize:] ==
208 samples for NSWindow frame setting
545 samples for *drawing* (CA::Transaction::commit())
~110 samples latency - waiting for event
10 samples in *validating* constraints
remainder in small posted tasks, autorelease pool draining (NSBitmapImageRep!)




minor contributors, but annoying

content::IsUseZoomForDSFEnabled()  -- called a lot. Does a std::map traversal (command line flags?)



 

Deleted: cocoa_window_resize.txt 1.2 MB

cocoa_window_resize.txt 1.2 MB View Download