632653 - Instrument shape creation and kinds (viz, indexed props, possibly in slow arrays)

Status: RESOLVED INCOMPLETE

(Core :: JavaScript Engine, defect)

Description

[Brendan Eich [:brendan]]

Spun off from bug 630456.

/be

Comment 1

[Nicholas Nethercote [inactive]]

More specifically: bug 630456 comment 26, which reads:

"I bet a lot of shapes come from (perhaps one or two) large slow arrays. We should not be using shapes for slow array elements, esp. if the array is dense but not quite dense enough to avoid being slow-ified. Can you measure?"

Comment 2

[Brendan Eich [:brendan]]

Please steal this bug.

/be

Comment 3

[Nicholas Nethercote [inactive]]

Brendan, what kind of instrumentation were you imagining?  For example, for bug 687935 I have a hacky patch that distinguishes three kinds of shapes in about:memory:

│   │  │   ├──4,558,784 B (02.74%) -- shapes
│   │  │   │  ├──4,185,792 B (02.51%) -- dict-int
│   │  │   │  ├────300,736 B (00.18%) -- normal
│   │  │   │  └─────72,256 B (00.04%) -- dict

where "dict-int" means "dictionary mode shapes with an integer propid".  I'm not sure if the dict/dict-int split is worth having as a permanent feature.  Are there other kinds of shapes you think are worth distinguishing?