827945 - Add SAMPLE_LABEL's in text layout code

Status: NEW

(Core :: Layout: Text and Fonts, defect)

Description

[Benoit Jacob [:bjacob] (mostly away)]

Attachment: Add SAMPLE_LABEL's

In bug 825622 we have profiles showing time spent in text layout code, but without more SAMPLE_LABEL's, it's hard to make precise sense of profiles. This patch allows to replace the mostly flat profile http://people.mozilla.com/~bgirard/cleopatra/#report=75848aa8ceae25cbd7e49ba1518793cdcc2156bb by the tree-view profile http://people.mozilla.com/~bgirard/cleopatra/#report=aaafd649dff13e7e1476991d0506cafe7e264258 .

Who should review this? Defaulting to dbaron.

Note: SAMPLE_LABEL has a cost, which is why I only put it in functions that looked expensive enough to offset that cost.

Maybe BenWa can comment in more detail about that cost.

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Comment on attachment 699352 [details] [diff] [review]
Add SAMPLE_LABEL's

Transferring review to roc, who knows this code better (though he may wish to transfer it, or parts of it, further); I'm a little concerned about whether some of these SAMPLE_LABELs might be in functions that are too short... thus distorting the numbers.

Comment 2

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Yeah, these feel too fine-grained ... but it's hard to say exactly what "too fine-grained" means. Do we have data to go by?

Though I think, for main-thread-only labels like these, we could have a SAMPLE_LABEL_MAIN_THREAD that is very low overhead.