Use small page size/flags for Sparse Virtual Memory

Currently Sparse Virtual Memory uses page size Object Heap is allocated
with. We want to use small pages for Sparse Heap always regardless. Also
Sparse Virtual Memory uses page flags "requested" for Object Heap. This
is the bug. Page flags should be paired with the page size.

Please note, that current MM_SparseVirtualMemory implementation can use
double mapping instead of off-heap. This is an experimental feature
never used in the code and not planned to be used. This feature uses
hidden assumption that memory page size/flags should be the same for
Object and Sparse heaps. This PR can break it potentially in the case
memory page settings in the Object Heap and Sparse heap are different.
We are going to be aware about this if we need another round of
experimental testing with double mapping support.

Signed-off-by: Dmitri Pivkine <[email protected]>

gc/base/GCExtensionsBase.cpp

@@ -135,6 +135,10 @@ MM_GCExtensionsBase::initialize(MM_EnvironmentBase* env)
 	gcmetadataPageSize = pageSizes[0];
 	gcmetadataPageFlags = OMRPORT_VMEM_PAGE_FLAG_NOT_USED;
 
+	sparseHeapPageSize = pageSizes[0];
+	sparseHeapPageFlags = OMRPORT_VMEM_PAGE_FLAG_NOT_USED;
+
+
 #define SIXTY_FOUR_KB	((uintptr_t)64 * 1024)
 #define ONE_MB			((uintptr_t)1 * 1024 * 1024)
 #define TWO_MB			((uintptr_t)2 * 1024 * 1024)
@@ -160,6 +164,10 @@ MM_GCExtensionsBase::initialize(MM_EnvironmentBase* env)
 		gcmetadataPageFlags = pageFlags[0];
 	}
 
+	if (!validateDefaultPageParameters(sparseHeapPageSize, sparseHeapPageFlags, pageSizes, pageFlags)) {
+		sparseHeapPageSize = pageSizes[0];
+		sparseHeapPageFlags = pageFlags[0];
+	}
 
 	if (!_forge.initialize(env->getPortLibrary())) {
 		goto failed;

gc/base/GCExtensionsBase.hpp

@@ -281,10 +281,13 @@ class MM_GCExtensionsBase : public MM_BaseVirtual {
 #endif /* OMR_GC_DOUBLE_MAP_ARRAYLETS */
 	bool isVirtualLargeObjectHeapRequested;
 	bool isVirtualLargeObjectHeapEnabled;
-	uintptr_t requestedPageSize;
-	uintptr_t requestedPageFlags;
-	uintptr_t gcmetadataPageSize;
-	uintptr_t gcmetadataPageFlags;
+
+	uintptr_t requestedPageSize;	/**< Memory page size for Object Heap */
+	uintptr_t requestedPageFlags;	/**< Memory page flags for Object Heap */
+	uintptr_t gcmetadataPageSize;	/**< Memory page size for GC Meta data */
+	uintptr_t gcmetadataPageFlags;	/**< Memory page flags for GC Meta data */
+	uintptr_t sparseHeapPageSize;	/**< Memory page size for Sparse Object Heap */
+	uintptr_t sparseHeapPageFlags;	/**< Memory page flags for Sparse Object Heap */
 
 #if defined(OMR_GC_MODRON_SCAVENGER)
 	MM_SublistPool rememberedSet;
@@ -1516,6 +1519,8 @@ class MM_GCExtensionsBase : public MM_BaseVirtual {
 		, requestedPageFlags(OMRPORT_VMEM_PAGE_FLAG_NOT_USED)
 		, gcmetadataPageSize(0)
 		, gcmetadataPageFlags(OMRPORT_VMEM_PAGE_FLAG_NOT_USED)
+		, sparseHeapPageSize(0)
+		, sparseHeapPageFlags(OMRPORT_VMEM_PAGE_FLAG_NOT_USED)
 #if defined(OMR_GC_MODRON_SCAVENGER)
 		, rememberedSet()
 		, oldHeapSizeOnLastGlobalGC(UDATA_MAX)

gc/base/SparseVirtualMemory.cpp

@@ -45,14 +45,15 @@
  ****************************************
  */
 
-MM_SparseVirtualMemory*
+MM_SparseVirtualMemory *
 MM_SparseVirtualMemory::newInstance(MM_EnvironmentBase* env, uint32_t memoryCategory, MM_Heap *in_heap)
 {
+	MM_GCExtensionsBase *extensions = env->getExtensions();
 	MM_SparseVirtualMemory* vmem = NULL;
 	vmem = (MM_SparseVirtualMemory*)env->getForge()->allocate(sizeof(MM_SparseVirtualMemory), OMR::GC::AllocationCategory::FIXED, OMR_GET_CALLSITE());
 
 	if (vmem) {
-		new (vmem) MM_SparseVirtualMemory(env, in_heap->getPageSize(), in_heap);
+		new (vmem) MM_SparseVirtualMemory(env, extensions->sparseHeapPageSize, extensions->sparseHeapPageFlags, in_heap);
 		if (!vmem->initialize(env, memoryCategory)) {
 			vmem->kill(env);
 			vmem = NULL;

gc/base/SparseVirtualMemory.hpp

@@ -84,8 +84,8 @@ class MM_SparseVirtualMemory : public MM_VirtualMemory {
 	bool initialize(MM_EnvironmentBase* env, uint32_t memoryCategory);
 	void tearDown(MM_EnvironmentBase *env);
 
-	MM_SparseVirtualMemory(MM_EnvironmentBase* env, uintptr_t pageSize, MM_Heap *in_heap)
-		: MM_VirtualMemory(env, env->getExtensions()->heapAlignment, pageSize, env->getExtensions()->requestedPageFlags, 0, OMRPORT_VMEM_MEMORY_MODE_READ | OMRPORT_VMEM_MEMORY_MODE_WRITE)
+	MM_SparseVirtualMemory(MM_EnvironmentBase* env, uintptr_t pageSize, uintptr_t pageFlags, MM_Heap *in_heap)
+		: MM_VirtualMemory(env, env->getExtensions()->heapAlignment, pageSize, pageFlags, 0, OMRPORT_VMEM_MEMORY_MODE_READ | OMRPORT_VMEM_MEMORY_MODE_WRITE)
 		, _heap(in_heap)
 		, _sparseDataPool(NULL)
 		, _largeObjectVirtualMemoryMutex(NULL)