[feature] Switch from Java's G1 to Z Garbage Collector

Author: adamretter

exist-distribution/pom.xml

@@ -776,12 +776,15 @@
                     </binFileExtensions>
                     <defaultJvmSettings>
                         <initialMemorySize>128m</initialMemorySize>
+                        <extraArguments>
+                            <extraArgument>-XX:+UseNUMA</extraArgument>
+                            <extraArgument>-XX:+UseZGC</extraArgument>
+                            <extraArgument>-XX:+UseStringDeduplication</extraArgument>
 
-                        <!-- Option to generate JDWP debuggable app -->
-                        <!-- extraArguments>
-                            <extraArgument>-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005</extraArgument>
-                        </extraArguments -->
+                            <!-- Option to generate JDWP debuggable app -->
+                            <!-- extraArgument>-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005</extraArgument -->
 
+                        </extraArguments>
                         <systemProperties>
                             <systemProperty>file.encoding=UTF-8</systemProperty>
                             <systemProperty>log4j.configurationFile=@BASEDIR@/etc/log4j2.xml</systemProperty>

exist-docker/src/main/resources-filtered/Dockerfile

@@ -80,7 +80,8 @@ ENV JAVA_TOOL_OPTIONS \
   -Dexist.configurationFile=/exist/etc/conf.xml \
   -Djetty.home=/exist \
   -Dexist.jetty.config=/exist/etc/jetty/standard.enabled-jetty-configs \
-  -XX:+UseG1GC \
+  -XX:+UseNUMA \
+  -XX:+UseZGC \
   -XX:+UseStringDeduplication \
   -XX:+UseContainerSupport \
   -XX:MaxRAMPercentage=${JVM_MAX_RAM_PERCENTAGE:-75.0} \

exist-docker/src/main/resources-filtered/Dockerfile-DEBUG

@@ -65,7 +65,8 @@ ENV JAVA_TOOL_OPTIONS \
   -Dexist.configurationFile=/exist/etc/conf.xml \
   -Djetty.home=/exist \
   -Dexist.jetty.config=/exist/etc/jetty/standard.enabled-jetty-configs \
-  -XX:+UseG1GC \
+  -XX:+UseNUMA \
+  -XX:+UseZGC \
   -XX:+UseStringDeduplication \
   -XX:+UseContainerSupport \
   -XX:MaxRAMPercentage=${JVM_MAX_RAM_PERCENTAGE:-75.0} \

exist-docker/src/main/resources-filtered/README.md

@@ -297,9 +297,9 @@ docker run -m 600m …
 ```
 
 Lastly, this image uses a new garbage collection mechanism 
-[garbage first (G1)](https://docs.oracle.com/javase/9/gctuning/garbage-first-garbage-collector.htm#JSGCT-GUID-ED3AB6D3-FD9B-4447-9EDF-983ED2F7A573) `-XX:+UseG1GC` 
+[The Z Garbage Collector (https://docs.oracle.com/en/java/javase/11/gctuning/z-garbage-collector1.html)] `-XX:+UseZGC`
 and [string deduplication](http://openjdk.java.net/jeps/192) `-XX:+UseStringDeduplication` to improve performance.
 
 To disable or further tweak these features edit the relevant parts of the `Dockerfile`, or when running the image. 
 As always when using the latest and greatest, YMMV. 
-Feedback about real world experiences with this features in connection with eXist-db is very much welcome.
+Feedback about real world experiences with these features in connection with eXist-db is very much welcome.