[Truffle] Make global variables constants if they are rarely changed.

jruby · Jun 25, 2016 · e04278d · e04278d
1 parent bc4b492
commit e04278d
Showing 7 changed files with 91 additions and 8 deletions.
diff --git a/core/src/main/java/org/jruby/util/cli/Options.java b/core/src/main/java/org/jruby/util/cli/Options.java
@@ -248,6 +248,9 @@ public class Options {
     public static final Option<Boolean> TRUFFLE_ROPE_LAZY_SUBSTRINGS = bool(TRUFFLE, "truffle.rope.lazy_substrings", true, "Indicates whether a substring operation on a rope should be performed lazily.");
     public static final Option<Boolean> TRUFFLE_ROPE_PRINT_INTERN_STATS = bool(TRUFFLE, "truffle.rope.print_intern_stats", false, "Print interned rope stats at application exit.");
 
+    public static final Option<Integer> TRUFFLE_GLOBAL_VARIABLE_MAX_INVALIDATIONS = integer(TRUFFLE, "truffle.global_variable.max_invalidations", 10,
+            "Maximum number of times a global variable can be changed to be considered constant.");
+
     public static final Option<Integer> TRUFFLE_DEFAULT_CACHE = integer(TRUFFLE, "truffle.default_cache", 8, "Default size for caches.");
 
     public static final Option<Integer> TRUFFLE_METHOD_LOOKUP_CACHE = integer(TRUFFLE, "truffle.method_lookup.cache", TRUFFLE_DEFAULT_CACHE.load(), "Method lookup cache size.");

diff --git a/test/truffle/compiler/pe/language/global_pe.rb b/test/truffle/compiler/pe/language/global_pe.rb
@@ -0,0 +1,22 @@
+# Copyright (c) 2014, 2016 Oracle and/or its affiliates. All rights reserved. This
+# code is released under a tri EPL/GPL/LGPL license. You can use it,
+# redistribute it and/or modify it under the terms of the:
+#
+# Eclipse Public License version 1.0
+# GNU General Public License version 2
+# GNU Lesser General Public License version 2.1
+
+$stable_global = 42
+
+example "$stable_global", 42
+
+$almost_stable_global = 1
+$almost_stable_global = 2
+
+example "$almost_stable_global", 2
+
+100.times { |i|
+  $unstable_global = i
+}
+
+counter example "$unstable_global"
diff --git a/truffle/src/main/java/org/jruby/truffle/core/CoreLibrary.java b/truffle/src/main/java/org/jruby/truffle/core/CoreLibrary.java
@@ -1315,11 +1315,11 @@ public GlobalVariables getGlobalVariables() {
     }
 
     public DynamicObject getLoadPath() {
-        return (DynamicObject) loadPathStorage.value;
+        return (DynamicObject) loadPathStorage.getValue();
     }
 
     public DynamicObject getLoadedFeatures() {
-        return (DynamicObject) loadedFeaturesStorage.value;
+        return (DynamicObject) loadedFeaturesStorage.getValue();
     }
 
     public DynamicObject getMainObject() {

diff --git a/truffle/src/main/java/org/jruby/truffle/language/globals/GlobalVariableStorage.java b/truffle/src/main/java/org/jruby/truffle/language/globals/GlobalVariableStorage.java
@@ -10,10 +10,60 @@
 
 package org.jruby.truffle.language.globals;
 
+import com.oracle.truffle.api.Assumption;
+import com.oracle.truffle.api.CompilerDirectives;
+import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
+import com.oracle.truffle.api.utilities.CyclicAssumption;
+import org.jruby.util.cli.Options;
+
 public class GlobalVariableStorage {
-    public volatile Object value;
+
+    private static final int GLOBAL_VARIABLE_MAX_INVALIDATIONS = Options.TRUFFLE_GLOBAL_VARIABLE_MAX_INVALIDATIONS.load();
+
+    private final CyclicAssumption unchangedAssumption = new CyclicAssumption("global variable unchanged");
+    private int changes = 0;
+
+    // This really means @CompilationFinal for compilation and volatile in interpreter
+    @CompilationFinal private volatile boolean assumeConstant = true;
+
+    private volatile Object value;
 
     GlobalVariableStorage(Object value) {
         this.value = value;
     }
+
+    public Object getValue() {
+        return value;
+    }
+
+    public Assumption getUnchangedAssumption() {
+        return unchangedAssumption.getAssumption();
+    }
+
+    public void setValue(Object value) {
+        if (assumeConstant) {
+            if (value != this.value) {
+                CompilerDirectives.transferToInterpreterAndInvalidate();
+                this.value = value;
+
+                synchronized (this) {
+                    if (!assumeConstant) {
+                        // Compiled code didn't see that we do not assumeConstant anymore
+                        return;
+                    }
+
+                    if (changes <= GLOBAL_VARIABLE_MAX_INVALIDATIONS) {
+                        changes++;
+                        unchangedAssumption.invalidate();
+                    } else {
+                        unchangedAssumption.getAssumption().invalidate();
+                        assumeConstant = false;
+                    }
+                }
+            }
+        } else {
+            this.value = value;
+        }
+    }
+
 }
diff --git a/truffle/src/main/java/org/jruby/truffle/language/globals/GlobalVariables.java b/truffle/src/main/java/org/jruby/truffle/language/globals/GlobalVariables.java
@@ -35,7 +35,7 @@ public Object getOrDefault(String key, Object defaultValue) {
     }
 
     public Object get(String key) {
-        return getStorage(key).value;
+        return getStorage(key).getValue();
     }
 
     @TruffleBoundary
@@ -52,7 +52,7 @@ public GlobalVariableStorage getStorage(String key) {
 
     public GlobalVariableStorage put(String key, Object value) {
         GlobalVariableStorage storage = getStorage(key);
-        storage.value = value;
+        storage.setValue(value);
         return storage;
     }
 
@@ -64,7 +64,7 @@ public Collection<DynamicObject> dynamicObjectValues() {
         final Collection<GlobalVariableStorage> storages = variables.values();
         final ArrayList<DynamicObject> values = new ArrayList<>(storages.size());
         for (GlobalVariableStorage storage : storages) {
-            final Object value = storage.value;
+            final Object value = storage.getValue();
             if (value instanceof DynamicObject) {
                 values.add((DynamicObject) value);
             }

diff --git a/truffle/src/main/java/org/jruby/truffle/language/globals/ReadGlobalVariableNode.java b/truffle/src/main/java/org/jruby/truffle/language/globals/ReadGlobalVariableNode.java
@@ -25,9 +25,16 @@ public ReadGlobalVariableNode(RubyContext context, SourceSection sourceSection,
         this.name = name;
     }
 
+    @Specialization(assumptions = "storage.getUnchangedAssumption()")
+    public Object readConstant(
+            @Cached("getStorage()") GlobalVariableStorage storage,
+            @Cached("storage.getValue()") Object value) {
+        return value;
+    }
+
     @Specialization
     public Object read(@Cached("getStorage()") GlobalVariableStorage storage) {
-        return storage.value;
+        return storage.getValue();
     }
 
     protected GlobalVariableStorage getStorage() {

diff --git a/truffle/src/main/java/org/jruby/truffle/language/globals/WriteGlobalVariableNode.java b/truffle/src/main/java/org/jruby/truffle/language/globals/WriteGlobalVariableNode.java
@@ -24,7 +24,8 @@ public abstract class WriteGlobalVariableNode extends RubyNode {
 
     @Specialization
     public Object write(Object value, @Cached("getStorage()") GlobalVariableStorage storage) {
-        return storage.value = value;
+        storage.setValue(value);
+        return value;
     }
 
     protected GlobalVariableStorage getStorage() {