Bug 189156 – [JSC] Clean up StructureStubClearingWatchpoint

• Status: RESOLVED
• Resolution: FIXED
• Component: New Bugs

[Yusuke Suzuki]

[JSC] Clean up StructureStubClearingWatchpoint

[Yusuke Suzuki]

Created attachment 348502 [details]
Patch

[Saam Barati]

Comment on attachment 348502 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=348502&action=review

> Source/JavaScriptCore/bytecode/StructureStubClearingWatchpoint.h:-96
> -    std::unique_ptr<StructureStubClearingWatchpoint> m_head;

Was there a reason for the old code?

[Yusuke Suzuki]

Comment on attachment 348502 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=348502&action=review

>> Source/JavaScriptCore/bytecode/StructureStubClearingWatchpoint.h:-96
>> -    std::unique_ptr<StructureStubClearingWatchpoint> m_head;
> 
> Was there a reason for the old code?

I can't see any reason. Vector<StructureStubClearingWatchpoint> is bad since each StructureStubClearingWatchpoint address can be changed. But Vector<std::unique_ptr<StructureStubClearingWatchpoint>> is enough.

[Saam Barati]

Comment on attachment 348502 [details]
Patch

Maybe the linked list uses less memory on average for common programs?

[Yusuke Suzuki]

(In reply to Saam Barati from comment #4)
> Comment on attachment 348502 [details]
> Patch
> 
> Maybe the linked list uses less memory on average for common programs?

In the Vector<> case, we can drop a link in StructureStubClearingWatchpoint instead of allocating storage for Vector.
The memory consumption is so-so, larger in Vector case due to unused memory allocation for storages, or larger in linked-list case due to the representation of the enlarged objects in bmalloc (it depends on whether the given object size would fit to the bmalloc's segregated heap).
We can use Bag<> here, it does not change memory usage. Changed.

[Yusuke Suzuki]

(In reply to Yusuke Suzuki from comment #5)
> (In reply to Saam Barati from comment #4)
> > Comment on attachment 348502 [details]
> > Patch
> > 
> > Maybe the linked list uses less memory on average for common programs?
> 
> In the Vector<> case, we can drop a link in StructureStubClearingWatchpoint
> instead of allocating storage for Vector.
> The memory consumption is so-so, larger in Vector case due to unused memory
> allocation for storages, or larger in linked-list case due to the
> representation of the enlarged objects in bmalloc (it depends on whether the
> given object size would fit to the bmalloc's segregated heap).
> We can use Bag<> here, it does not change memory usage. Changed.

If allocations of this watchpoint in this vector/bag is so many, SegmentedVector<> can improve memory usage more. In the meantime, I'll use bag.

[Yusuke Suzuki]

Created attachment 348708 [details]
Patch

[Yusuke Suzuki]

Ping?

[Saam Barati]

Comment on attachment 348708 [details]
Patch

r=me

[Yusuke Suzuki]

(In reply to Saam Barati from comment #9)
> Comment on attachment 348708 [details]
> Patch
> 
> r=me

Thanks!

[Yusuke Suzuki]

Committed r235776: <https://trac.webkit.org/changeset/235776>

[Radar WebKit Bug Importer]

<rdar://problem/44211170>