1314821 - debugger and console are extremely slow to show the contents of a large typed array

Status: NEW

(DevTools :: Shared Components, defect)

Description

[Daniel Brooks [:db48x]]

Attachment: slow-debugger.html

In the attached testcase, showing the HEAP8 variable in either the console or in the debugger takes quite a long time. I noticed this in a much more complicated case where I was inspecting an object that had half a dozen such large typed arrays; it took several minutes to display the contents of the object. The time it takes appears to be proportional to the length of the array, which is especially annoying since the debugger is going to shorten it significantly once it displays it.

Comment 1

[Lin Clark [:linclark]]

If you were testing with new console/debugger, this may be related to Bug 1313161.

Comment 2

[Daniel Brooks [:db48x]]

Oh, I forgot to mention memory usage. Watching this in top shows the content process passing 8GB RSS while rendering this value, then dropping back to a few hundred megs when it's done.

Comment 3

[Brian Grinstead [:bgrins]]

What version are you testing in?  We had a similar issue fixed in 49: Bug 1270179

Comment 4

[Daniel Brooks [:db48x]]

(In reply to Brian Grinstead [:bgrins] from comment #3)
> What version are you testing in?  We had a similar issue fixed in 49: Bug
> 1270179

Trunk, as indicated. Specifically a nightly from this morning (20161102030205).

Comment 5

[Julien Cristau [:jcristau]]

Mass wontfix for bugs affecting firefox 52.