563711 - Optimize nsHTMLContentSerializer::AppendAndTranslateEntities

Status: RESOLVED FIXED

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

Description

[Olli Pettay [:smaug][[e-mail]]]

Attachment: testcase

If there are lots of entities to translate, nsHTMLContentSerializer::AppendAndTranslateEntities takes
way too much time of ::GetInnerHTML (like 66%).
String modifications and memory (de)allocation are the ones which take
most of the time.

Comment 1

[Laurent Jouanneau]

I'm trying to do something.

Comment 2

[Laurent Jouanneau]

Attachment: wip

The result of the test on my computer with the current trunk is: total: 91999, avg 183.998
with this patch: total: 84945, avg 169.89

It's better, but not as better than safari: total: 63616, avg 127.232

Olli, do you have ideas for other improvements ?

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Well, we should improve string handling in serializers in general, but in this 
particular case I think AppendASCIItoUTF16 is pretty heavy.
It needs to increase the capacity of aOutputStr all the time.

So, perhaps collecting strings to some array and then call
SetCapacity on the aOutputStr only once after loops and then Append strings to 
aOutputStr could help, maybe.

Comment 4

[Olli Pettay [:smaug][[e-mail]]]

Also, I think string.AppendASCII(ascii) is actually faster than 
AppendASCIItoUTF16(ascii, string).
The latter one creates some extra temporary string objects.
I wonder if there is some other difference in the behavior.

Comment 5

[Olli Pettay [:smaug][[e-mail]]]

Another testcase is in bug 561717

Comment 6

[Olli Pettay [:smaug][[e-mail]]]

Laurent, do you want a review for the patch?
(gecko is already in many innerHTML cases faster than trunk webkit, and
would be great to get faster serializers. This would be one step.)

Comment 7

[Olli Pettay [:smaug][[e-mail]]]

Attachment: small fixes

This uses AppendASCII, which is faster and ok to use at least in this case.
Added also the missing Truncate call.

Comment 8

[Olli Pettay [:smaug][[e-mail]]]

Attachment: a bit simpler

Jonas, perhaps you could review this.

Comment 9

[Olli Pettay [:smaug][[e-mail]]]

http://hg.mozilla.org/mozilla-central/rev/1b59e562e0f0

Marking this fixed once this has passed the tests.