https://bz.apache.org/bugzilla/show_bug.cgi?id=69381
Bug ID: 69381
Summary: Excess object copying while evaluating reflective
method calls
Product: Tomcat 9
Version: 9.0.x
Hardware: PC
Status: NEW
Severity: normal
Priority: P2
Component: EL
Assignee: dev@tomcat.apache.org
Reporter: jeng...@amazon.com
Target Milestone: -----
Evaluating JSP EL expressions with reflective operations ("${beanA.getBean()}")
is slow because the reflective objects are copied on each execution.
Specifically, javax.el.Util.findMethod() calls java.lang.Class.getMethods().
In OpenJDK, getMethods() makes a call to duplicate the source-of-truth array.
>From OpenJDK source:
return copyMethods(privateGetPublicMethods());
An easy optimization would be to store the array in a ConcurrentHashMap for
later reuse; I'm not certain whether there are ways to use Class.getMethod() to
more specifically retrieve the targeted Method.
A local benchmark based on TestELParserPerformance shows that a
ConcurrentHashMap accelerates this expression 50% (from 1070ns to 500ns) and
reduces memory allocation by 75% (from 248MB to 64MB).
Static ConcurrentHashMaps have disadvantages, but this is a large impact,
especially on objects with many methods. The benchmark numbers above featured
8 Methods but tests with larger objects confirm a linear increase in memory
allocation and a sub-linear increase in runtime.
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