Merge pull request eclipse-openj9#8329 from eclipse/revert-8254-doubl…

…emap_huge

Revert "Disable double mapping when page size exceeds default page size"

runtime/gc_base/IndexableObjectAllocationModel.hpp

@@ -1,6 +1,6 @@
 
 /*******************************************************************************
- * Copyright (c) 1991, 2020 IBM Corp. and others
+ * Copyright (c) 1991, 2019 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -128,13 +128,7 @@ class MM_IndexableObjectAllocationModel : public MM_JavaObjectAllocationModel
 	/**
 	 * For non-contiguous arraylets (discontiguous arraylets, hybrid not allowed
 	 * when double map is enabled), double maps the arraylet leaves to a contiguous
-	 * region outside the heap, making a discontiguous arraylet look contiguous.
-	 * Currently double map is enabled by manually passing command line option
-	 * XXgc:enableDoubleMapping; however, if the system supports huge pages and
-	 * double map gets manually enabled, then double map will be disabled. That's
-	 * because double map does support huge pages yet. If one still wants to
-	 * enable double map in such systems, one must manually force the application
-	 * to use the small system page size
+	 * region outside the heap, making a discontiguous arraylet look contiguous
 	 *
 	 * @param env thread GC Environment
 	 * @param objectPtr indexable object spine

runtime/gc_glue_java/ArrayletObjectModelBase.hpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 1991, 2020 IBM Corp. and others
+ * Copyright (c) 1991, 2019 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -141,10 +141,8 @@ class GC_ArrayletObjectModelBase
 
 #if defined(J9VM_GC_ENABLE_DOUBLE_MAP)
 	/**
-	 * Sets enable double mapping status. Note that the double map
-	 * status value may differ from the requested one in certain
-	 * circuntances.
-	 *
+	 * Sets enable double mapping
+	 * 
 	 * @param enableDoubleMapping
 	 */
 	MMINLINE void
@@ -154,9 +152,9 @@ class GC_ArrayletObjectModelBase
 	}
 
 	/**
-	 * Returns enable double mapping status
+	 * Returns enable double mapping
 	 * 
-	 * @return true if double mapping status is set to true, false otherwise.
+	 * @return true if double mapping is enabled, false otherwise
 	 */
 	MMINLINE bool
 	isDoubleMappingEnabled()

runtime/gc_modron_startup/mmparseXXgc.cpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 1991, 2020 IBM Corp. and others
+ * Copyright (c) 1991, 2019 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -165,12 +165,12 @@ gcParseXXgcArguments(J9JavaVM *vm, char *optArg)
 			continue;
 		}
 #if defined(J9VM_GC_ENABLE_DOUBLE_MAP)
-		if (try_scan(&scan_start, "enableArrayletDoubleMapping")) {
-			extensions->isArrayletDoubleMapRequested = true;
+		if (try_scan(&scan_start, "enableDoubleMapping")) {
+			extensions->indexableObjectModel.setEnableDoubleMapping(true);
 			continue;
                 }
-		if (try_scan(&scan_start, "disableArrayletDoubleMapping")) {
-			extensions->isArrayletDoubleMapRequested = false;
+		if (try_scan(&scan_start, "disableDoubleMapping")) {
+			extensions->indexableObjectModel.setEnableDoubleMapping(false);
 			continue;
 		}
 #endif /* J9VM_GC_ENABLE_DOUBLE_MAP */

runtime/gc_vlhgc/ConfigurationIncrementalGenerational.cpp

@@ -1,6 +1,6 @@
 
 /*******************************************************************************
- * Copyright (c) 1991, 2020 IBM Corp. and others
+ * Copyright (c) 1991, 2019 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -97,20 +97,6 @@ MM_ConfigurationIncrementalGenerational::createHeapWithManager(MM_EnvironmentBas
 		return NULL;
 	}
 
-#if defined(J9VM_GC_ENABLE_DOUBLE_MAP)
-	/* Disable double map if requested page sizes used is equal to huge pages.
-	 * Currently double map is not supported when huge pages are used.
-	 * Note that we keep two double map fields: one for requested and another for
-	 * status. If large pages is enabled, it  will only change the STATUS of double
-	 * mapping, keeping the REQUESTED double mapping field intact.
-	 */
-	if (extensions->isArrayletDoubleMapRequested) {
-		if (!extensions->memoryManager->isLargePage(env, heap->getPageSize())) {
-			extensions->indexableObjectModel.setEnableDoubleMapping(true);
-		}
-	}
-#endif /* J9VM_GC_ENABLE_DOUBLE_MAP */
-
 	/* when we try to attach this heap to a region manager, we will need the card table since it needs to be NUMA-affinitized using the same logic as the heap so initialize it here */
 	extensions->cardTable = MM_IncrementalCardTable::newInstance(MM_EnvironmentVLHGC::getEnvironment(env), heap);
 	if (NULL == extensions->cardTable) {