Bug 160112 – REGRESSION (r202876): Web Inspector: Switching away from Console tab with a lot of messages is slow

• Status: RESOLVED
• Resolution: FIXED
• Component: Web Inspector

[Nikita Vasilyev]

Created attachment 284396 [details]
[HTML] Reduction

This regressed in:
https://trac.webkit.org/changeset/202876/trunk/Source/WebInspectorUI/UserInterface/Views/TabBrowser.js

Steps:
1. Open attached reduction
2. Open Web Inspector
3. Open Console tab
4. Clear console
5. Reload the page
6. Click on Debugger tab

Expected:
Debugger tab opens in <0.5 seconds

Actual:
Web Inspector UI becomes unresponsive for 2-3 seconds before it opens Debugger tab.


rdar://problem/27431121

[Nikita Vasilyev]

Created attachment 284397 [details]
Patch

[Nikita Vasilyev]

Created attachment 284399 [details]
[Image] Before/After

[Nikita Vasilyev]

With the patch applied, I was unable to reproduce bug 158069.
cq- because I don't yet understand the change that was made in that bug.

[Nikita Vasilyev]

(In reply to comment #2)
> Created attachment 284399 [details]
> [Image] Before/After

Hm, I'm getting different results every time.
I'm still seeing 2-3x performance improvement on average.

[Joseph Pecoraro]

Comment on attachment 284397 [details]
Patch

r=me, Tim's review comment at the time made this change unnecessary anyways, so win win!

[Joseph Pecoraro]

Comment on attachment 284397 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=284397&action=review

> Source/WebInspectorUI/ChangeLog:11
> +        (WebInspector.TabBrowser.prototype._tabBarItemSelected):
> +        Showing NavigationSidebar before removing previous TabContentView can be very slow when
> +        TabContentView is ConsoleTabContentView with a lot of messages.

This comment just says "can be slow" but doesn't state the reason WHY it is slow.

In this case, I believe the WHY was because it caused extra forced layouts because of the order of operations (show sidebar, change content view, show sidebar) instead of (change content view, show sidebar, show sidebar).

[Nikita Vasilyev]

Created attachment 284403 [details]
Patch

[Joseph Pecoraro]

Comment on attachment 284403 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=284403&action=review

> Source/WebInspectorUI/ChangeLog:9
> +        TabContentView is ConsoleTabContentView with a lot of messages because of the order of operations:

Again "because of the order of operations" doesn't explain what is slow. It is because this different order of operations triggered MORE forced layouts.

[Nikita Vasilyev]

Created attachment 284404 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 284404 [details]
Patch

Clearing flags on attachment: 284404

Committed r203636: <http://trac.webkit.org/changeset/203636>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.