1525953 - make log module creation better

Status: RESOLVED FIXED

(Core :: XPCOM, enhancement)

Description

[Nathan Froyd [:froydnj]]

This doesn't improve actually fetching already-created log modules, but it will
make their point of creation slightly faster and eliminates a little bit of
process memory to boot.

Comment 1

[Nathan Froyd [:froydnj]]

Attachment: part 1 - enforce that LazyLogModule names are compile-time constants

They are already, and ensuring this means that we can remove some
allocations in later patches.

Comment 2

[Nathan Froyd [:froydnj]]

Attachment: part 2 - don't duplicate strings in LogModuleManager's hash table

Now that log module names are guaranteed to be in static storage, we can
depend on them directly, rather than allocating storage for them in the
hash table.

Comment 3

[Nathan Froyd [:froydnj]]

Attachment: part 3 - don't duplicate strings in LogModule

The module name comes via LazyLogModule, which is guaranteed to have
statically-allocated names, so there's no reason we have to strdup here.

Comment 4

[Nathan Froyd [:froydnj]]

Attachment: part 4 - add LookupOrAddFrom method to nsClassHashtable

This is partially a workaround for C++'s visibility rules, but it might
also make a difference if constructor arguments are particularly
expensive to construct.  Having a lambda means that the evaluation of
those arguments can be delayed until necessary, unlike LookupOrAdd.

Comment 5

[Nathan Froyd [:froydnj]]

Attachment: part 5 - use LookupOrAddFrom when getting log modules

No reason to do the hash lookup twice here.

Comment 6

[Nathan Froyd [:froydnj]]

Comment on attachment 9042172 [details] [diff] [review]
part 2 - don't duplicate strings in LogModuleManager's hash table

Ugh, we can't do this because you can pass in dynamic module names via preferences and such.

Comment 7

[Nathan Froyd [:froydnj]]

Comment on attachment 9042173 [details] [diff] [review]
part 3 - don't duplicate strings in LogModule

Same problem as with part 2, though maybe you could get this to be tied to the lifetime of the hash key, and reuse the same thing for both?

Comment 8

[Eric Rahm [:erahm]]

Comment on attachment 9042171 [details] [diff] [review]
part 1 - enforce that LazyLogModule names are compile-time constants

Clearing reviews for now, I don't think this is ready yet. Let me know if you want me to review other parts.

Comment 9

[BugBot [:suhaib / :marco/ :calixte]]

The bug assignee didn't login in Bugzilla in the last 7 months, so the assignee is being reset.

Comment 10

[Nika Layzell [:nika] (ni? for response)]

The main change in this bug happened as one of the bulk changes in bug 1691894, so we can resolve this.