15416 - [perf] Massive performance problems

Status: VERIFIED FIXED

(Core :: DOM: Core & HTML, defect, P3)

Description

[troy]

The attachment shows a HTML file I got from Kipp that takes a very long time to
load. It's not layout, because most everything is marked 'display' 'none'.
However, almost every element has three JavaScript handlers: onmouseout,
onmouseover, and onclick.

As the following information from Quantify indicates that's causing huge amounts
of heap allocations. Can't we do some of this lazily instead of when building
the content model?

It seems that nsEventListenerManager::AddScriptEventListener is called 8,889
times (by the nsGenericHTMLElement::SetAttribute code) and that causes us to
call JS_CompileUCFunctionForPrincipals and from then on we're doomed.

Quantify shows 394,248 calls to HeapAlloc most of which are called by JS_malloc
and are the result of processing the various scripts. There are also 17,785
calls to JS_ArenaRelease as well.

I think the JavaScript code has some serious performance issues as well

Comment 1

[troy]

Attachment: Zip file with V0.html test case

Comment 2

[troy]

Fixed with Vidur's change to delay evaluation of the script until it is needed.

I confirmed that the page now loads very quickly

Comment 3

[Prashant Desale]

troy, would you like to verify this one ?

Comment 4

[Prashant Desale]

According to troy, this's been fixed so marking verified.