Bug 249873 – AX: Pre-size AXIsolatedObject::m_propertyMap to avoid unnecessary HashTable reallocations

• Status: RESOLVED
• Resolution: FIXED
• Component: Accessibility

[Tyler Wilcock]

AX: Pre-size AXIsolatedObject::m_propertyMap to avoid unnecessary HashTable reallocations

[Radar WebKit Bug Importer]

<rdar://problem/103687278>

[Tyler Wilcock]

Created attachment 464196 [details]
Patch

[chris fleizach]

Comment on attachment 464196 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=464196&action=review

> Source/WebCore/accessibility/isolatedtree/AXIsolatedObject.cpp:57
> +    m_propertyMap.reserveInitialCapacity(126);

Is there a way to calculate this number less manually

[Tyler Wilcock]

(In reply to chris fleizach from comment #3)
> Comment on attachment 464196 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=464196&action=review
> 
> > Source/WebCore/accessibility/isolatedtree/AXIsolatedObject.cpp:57
> > +    m_propertyMap.reserveInitialCapacity(126);
> 
> Is there a way to calculate this number less manually
I don't think so. We could do:

m_propertyMap.reserveInitialCapacity(static_cast<unsigned>(AXPropertyName::VisibleRows));

Where AXPropertyName::VisibleRows is the last member of the AXPropertyName enum class. But that would assume that every object has every property, which definitely isn't true, and would cause us to over-allocate the hashmap for every object.

[Tyler Wilcock]

> > Is there a way to calculate this number less manually
> I don't think so. We could do:
> 
> m_propertyMap.reserveInitialCapacity(static_cast<unsigned>(AXPropertyName::
> VisibleRows));
> 
> Where AXPropertyName::VisibleRows is the last member of the AXPropertyName
> enum class. But that would assume that every object has every property,
> which definitely isn't true, and would cause us to over-allocate the hashmap
> for every object.
Though we could probably do it if we had some structure that defined the properties for each type of object (i.e. something like WebAccessibilityObjectWrapperMac::accessibilityAttributeNames does), rather than the ad-hoc initialization we do now in AXIsolatedObject::initializeProperties.

But sizing the map based on such a structure would be invalidated by sparse property storage, too, so probably not worth the work to do.

[EWS]

Committed 258328@main (98a28389be81): <https://commits.webkit.org/258328@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 464196 [details].