559310 - [HTML5] nsHtml5TreeOpExecutor::FlushDocumentWrite() causes lots of nsTArray_base::ShrinkCapacity calls

Status: NEW

(Core :: DOM: HTML Parser, defect, P5)

Description

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

This shows up a bit in profiles when setting innerHTML.

Comment 1

[Johnny Stenback (:jst)]

Do you have any numbers for "a bit"?

Comment 2

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

IIRC it was 2-3%. I could re-profile tomorrow.

Comment 3

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

But it was certainly enough to get noticed.

Comment 4

[Henri Sivonen (:hsivonen)]

When the parser transfers tree ops from one queue to another, it tries to use nsTArray::Swap if the target array is empty. If the target array isn't empty, it uses nsTArray::MoveElementsFrom, which uses nsTArray::ShiftData to shift the source arrays elements to emptiness. I guess nsTArray needs to provide an option not to deallocate the backing buffer in that case.

Comment 5

[Jens Stutte [:jstutte]]

Bulk-downgrade of unassigned, >=5 years untouched DOM/Storage bugs' priority.

If you have reason to believe this is wrong (especially for the severity), please write a comment and ni :jstutte.