Disable explicit GC by default

We don't rely upon GC to cleanup mappedbytebuffers, we unmap them
explicitly on close in lucene. But the JDK has crazy loops with
explicit GCs in exceptional cases to try to force unmapping.

In general we don't want any of our code or library code calling
this method: so its banned in forbidden-apis as well.

bin/elasticsearch.in.sh

@@ -62,3 +62,6 @@ JAVA_OPTS="$JAVA_OPTS -XX:+HeapDumpOnOutOfMemoryError"
 # The path to the heap dump location, note directory must exists and have enough
 # space for a full heap dump.
 #JAVA_OPTS="$JAVA_OPTS -XX:HeapDumpPath=$ES_HOME/logs/heapdump.hprof"
+
+# Disables explicit GC
+JAVA_OPTS="$JAVA_OPTS -XX:+DisableExplicitGC"

core-signatures.txt

@@ -51,5 +51,8 @@ java.lang.Object#notifyAll()
 java.lang.Math#abs(int)
 java.lang.Math#abs(long)
 
+@defaultMessage Please do not try to stop the world
+java.lang.System#gc()
+
 @defaultMessage Use Long.compare instead we are on Java7
 com.google.common.primitives.Longs#compare(long,long)