[webkit-dev] Why so many text nodes in the DOM? (especially ones with just whitespace)

[David Hyatt]

On Jun 17, 2010, at 4:07 PM, Eric Seidel wrote:

> A does not follow from B in that sentence, that current memory
> fragmentation means we need to strip whitespace nodes.
> 

Yeah exactly.  Let's see some measurements that show the presence of these nodes are a real problem.

> It would also be possible to create a special shared "\n" text node,
> and have some sort of Copy On Write behavior.  Again, more complexity.
> Not sure if the complexity would be worth the perf win.
> 

There might be interesting tricks around this idea yeah.  Basically you want the common case of never really looking at the DOM from JS to result in efficient performance/memory use.  If walking the DOM then results in the creation of a more heavyweight whitespace Node, that would be fine I think.

The idea of trying to fold the information into Element is an interesting one.  Again I think we'd need measurements to see how much of a gain we'd typically get if we did this just for newlines for example, or if we'd need an optimization that extended to arbitrary whitespace sequences.  I tend to think the latter would be required (since cleanly indented HTML will have newlines and tabs and spaces for indentation in between elements).

I'm not particularly interested in a "break-the-web" mode that strips out those Nodes completely by default, since (a) breaking compatibility is bad and (b) nobody has shown me any evidence that these extra nodes are a problem on mobile devices.

An optimization that reduces memory use while preserving the correct behavior is much more appealing to me.

dave
(hyatt at apple.com)