JDK-8043605 : Enable history for empty property maps
  • Type: Enhancement
  • Component: core-libs
  • Sub-Component: jdk.nashorn
  • Affected Version: 9
  • Priority: P2
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2014-05-21
  • Updated: 2015-09-29
  • Resolved: 2014-05-21
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JDK 8 JDK 9
8u40Fixed 9 b17Fixed
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Description
JDK-8011540 disabled retaining of history for empty property maps. This unfortunately has the effect of creating a lot of new, semantically identical maps when an object's properties are populated dynamically (e.g. by reading key-value pairs from an array etc.) and thus subsequently producing megamorphic call sites. The histories are held as maps of (property->propertyMap), with properties held weakly and property maps held softly. These maps are mostly strongly held by other parts of the system, so they don't contribute to the memory pressure; the only thing contributing is the memory for the map itself.