JIT stops compiling after a while (java 8u45)

[Uwe Schindler]

Hi,

> >> For real world applications I hope that this is a much smaller issue but if
> you must load and execute loads and loads of short lived classes then it might
> be reasonable to disable concurrent class unloading (at the cost of getting
> serial Full gcs instead).
> >
> > Unfortunately, this is not a theoretical issue for us. We see this problem
> running Presto (http://prestodb.io), which generates bytecode for every
> query it processes. For now, we're working around it with a background
> thread that watches the size of the code cache and calls System.gc() when it
> gets close to the max
> (https://github.com/facebook/presto/commit/91e1b3bb6bbfffc62401025a24
> 231cd388992d7c).
> 
> Okay, I changed JDK-8023191 from enhancement to bug and set fix version to
> 9. We can then backport this to 8u.

Hi many thanks for taking care!

Apache Lucene's Expressions module (heavily used by Elasticsearch) also compiles small Java classes to execute custom document scoring operations that the user can supply, similar to Presto's SQL, as a Javascript-like formula that can work on arbitrary static double-parameter/double returning functions. These classes are loaded in a separate ClassLoader used solely for a single class and thrown away afterwards. In older Java versions GC was perfectly throwing away those classes...

Compiler & Classloader:
https://github.com/apache/lucene-solr/blob/master/lucene/expressions/src/java/org/apache/lucene/expressions/js/JavascriptCompiler.java

See tests like:
https://github.com/apache/lucene-solr/tree/master/lucene/expressions/src/test/org/apache/lucene/expressions/js

Uwe