805915 - More detail in JS memory reports

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Nicholas Nethercote [inactive]]

I have some patches to add yet more detail to JS memory reports.

Comment 1

[Nicholas Nethercote [inactive]]

Attachment: (part 1) - Rename the "cross-compartment-wrappers" memory report.

This patch renames the "cross-compartment-wrappers" memory report as
"cross-compartment-wrappers-table", which is a better name because it's just
the table, but not the CCW objects themselves.

Comment 2

[Nicholas Nethercote [inactive]]

Attachment: (part 2) - Add more detail to object memory reports.

This patch distinguishes dense array objects, slow array objects, and
cross-compartment wrapper objects from "ordinary" objects.

Comment 3

[Nicholas Nethercote [inactive]]

Attachment: (part 3) - Fix misleading behaviour of JSString::isShort().

JSString::isShort() succeeds for strings that are not short but happen to be
in a FINALIZE_SHORT_STRING arena.  This patch fixes this misleading behaviour.

Comment 4

[Nicholas Nethercote [inactive]]

Attachment: (part 4) - Add more detail to string memory reports.

This patch distinguishes short strings from normal strings.

Comment 5

[Luke Wagner [:luke]]

Comment on attachment 675641 [details] [diff] [review]
(part 3) - Fix misleading behaviour of JSString::isShort().

Thanks!

Comment 6

[Nicholas Nethercote [inactive]]

Attachment: (part 5) - Add more detail to shape memory reports.

This patch distinguishes tree shapes that don't have the global object as 
their parent.

Comment 7

[Luke Wagner [:luke]]

Comment on attachment 675645 [details] [diff] [review]
(part 4) - Add more detail to string memory reports.

Review of attachment 675645 [details] [diff] [review]:
-----------------------------------------------------------------

::: js/src/vm/String.h
@@ +415,4 @@
>  
>      static inline js::ThingRootKind rootKind() { return js::THING_ROOT_STRING; }
>  
> +    bool isShort() const;

Could you move this declaration next to the other isX() queries (below asInline, before asStable).

::: js/xpconnect/src/XPCJSRuntime.cpp
@@ +1509,5 @@
> +    CREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("gc-heap/strings/short"),
> +                     cStats.gcHeapStringsShort,
> +                     "Memory on the garbage-collected JavaScript "
> +                     "heap that holds short strings, in which the string "
> +                     "characters are stored in the string header.");

How about:

"Memory on the garbage-collected JavaScript heap that holds double-sized string headers which store the characters inline."

Comment 8

[Luke Wagner [:luke]]

Hmm, "double-sized" might be confusing (with the C++ type 'double').  How about "over-sized"?

Comment 9

[Luke Wagner [:luke]]

Comment on attachment 675646 [details] [diff] [review]
(part 5) - Add more detail to shape memory reports.

Review of attachment 675646 [details] [diff] [review]:
-----------------------------------------------------------------

::: js/xpconnect/src/XPCJSRuntime.cpp
@@ +1522,5 @@
> +    CREPORT_GC_BYTES(cJSPathPrefix + NS_LITERAL_CSTRING("gc-heap/shapes/tree/canonical"),
> +                     cStats.gcHeapShapesTreeCanonical,
> +                     "Memory on the garbage-collected JavaScript heap that "
> +                     "holds shapes that are in a property tree, and whose "
> +                     "parent is the global object.");

How about "Memory on the garbage-collected JavaScript heap that holds shapes that are in the property tree and represent an object whose parent is the global object" (and the same below, mutatis mutandis)?

Comment 10

[Nicholas Nethercote [inactive]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/22a934cbde1f
https://hg.mozilla.org/integration/mozilla-inbound/rev/31395c6bb9b8
https://hg.mozilla.org/integration/mozilla-inbound/rev/aa23bf4b9a20
https://hg.mozilla.org/integration/mozilla-inbound/rev/b23881c4de78
https://hg.mozilla.org/integration/mozilla-inbound/rev/7d95543f4750

Comment 11

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/22a934cbde1f
https://hg.mozilla.org/mozilla-central/rev/31395c6bb9b8
https://hg.mozilla.org/mozilla-central/rev/aa23bf4b9a20
https://hg.mozilla.org/mozilla-central/rev/b23881c4de78
https://hg.mozilla.org/mozilla-central/rev/7d95543f4750