lirui-apache commented on a change in pull request #10620:
[FLINK-15239][table-planner-blink] TM Metaspace memory leak
URL: https://github.com/apache/flink/pull/10620#discussion_r361088455
##########
File path:
flink-table/flink-table-runtime-blink/src/main/java/org/apache/flink/table/runtime/generated/CompileUtils.java
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@@ -45,7 +48,7 @@
* number of Meta zone GC (class unloading), resulting in performance
bottlenecks. So we add
* a cache to avoid this problem.
*/
- protected static final Cache<Tuple2<ClassLoader, String>, Class<?>>
COMPILED_CACHE = CacheBuilder
+ protected static final Cache<String, Cache<ClassLoader, Class>>
COMPILED_CACHE = CacheBuilder
.newBuilder()
.maximumSize(100) // estimated cache size
Review comment:
My hunch is that using soft values in the inner cache gives us fine grained
garbage collection. Instead of removing the whole inner cache, we may want to
only remove the least recently used class instances.
According to this
[reading](http://jeremymanson.blogspot.com/2009/07/how-hotspot-decides-to-clear_07.html),
the timestamp that a soft value was lastly accessed plays a part when JVM
decides whether to clear the reference.
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