JRuby CRIU proof-of-concept patch

jruby_criu.patch

commit dac864582a44da0017fdc5b85d431c05f40eb675
Author: Charles Oliver Nutter <headius@headius.com>
Date:   Sat Apr 22 12:40:27 2023 -0500

    criu testing

diff --git a/bin/jruby.sh b/bin/jruby.sh
index 00903f0ba8..fd62212a07 100755
--- a/bin/jruby.sh
+++ b/bin/jruby.sh
@@ -535,6 +535,8 @@ do
         --environment) print_environment_log=true ;;
         # warn but ignore
         --1.8|--1.9|--2.0) echo "warning: $1 ignored" 1>&2 ;;
+       --checkpoint) append java_args -Djruby.checkpoint.path=./jruby_criu -XX:+EnableCRIUSupport ;;
+       --restore) exec criu restore -D ./jruby_criu --shell-job -v4 --log-file=restore.log ;;
         # Abort processing on the double dash
         --) break ;;
         # Other opts go to ruby
diff --git a/core/src/main/java/org/jruby/Main.java b/core/src/main/java/org/jruby/Main.java
index a7b9e2935f..3f9c66594d 100644
--- a/core/src/main/java/org/jruby/Main.java
+++ b/core/src/main/java/org/jruby/Main.java
@@ -56,6 +56,7 @@ import java.io.*;
 import java.lang.management.ManagementFactory;
 import java.lang.management.RuntimeMXBean;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -63,6 +64,8 @@ import java.util.Set;
 import java.util.HashSet;
 import java.util.Properties;
 
+import org.eclipse.openj9.criu.CRIUSupport;
+
 /**
  * Class used to launch the interpreter.
  * This is the main class as defined in the jruby.mf manifest.
@@ -195,6 +198,31 @@ public class Main {
             main = new Main(true);
         }
 
+        if (System.getProperty("jruby.checkpoint.path") != null) {
+           // delete property since it is unknown to the rest of JRuby
+           String path = System.getProperty("jruby.checkpoint.path");
+           System.clearProperty("jruby.checkpoint.path");
+
+            // run a bunch of JRuby stuff and then checkpoint
+            if (CRIUSupport.isCRIUSupportEnabled()) {
+               System.out.print("Warming up JRuby...");
+                for (int i = 0; i < 100; i++) {
+                    Ruby.newInstance();
+                }
+               System.out.println(" done! Saving checkpoint.");
+
+                new CRIUSupport(Paths.get(path))
+                        .setLeaveRunning(false)
+                        .setShellJob(true)
+                        .setFileLocks(true)
+                        .setLogLevel(4)
+                        .setLogFile("logs")
+                        .checkpointJVM();
+            } else {
+                System.err.println("CRIU is not enabled: " + CRIUSupport.getErrorMessage());
+            }
+        }
+
         try {
             Status status = main.run(args);