Introduce Flush Caches For GC hook

It will trigger before flushing itself, so that users can report or process stats for various application thread caches before they are cleared. Signed-off-by: Aleksandar Micic <[email protected]>
dmitripivkine · Mar 1, 2024 · ced2f45 · ced2f45
1 parent f9174a0
commit ced2f45
Show file tree

Hide file tree

Showing 2 changed files with 35 additions and 14 deletions.
diff --git a/gc/base/OMRVMInterface.cpp b/gc/base/OMRVMInterface.cpp
@@ -46,17 +46,17 @@ extern "C" {
  * Actions required prior to walking the heap.
  */
 void
-hookWalkHeapStart(J9HookInterface** hook, uintptr_t eventNum, void* eventData, void* userData)
+hookWalkHeapStart(J9HookInterface **hook, uintptr_t eventNum, void *eventData, void *userData)
 {
-	MM_WalkHeapStartEvent* event = (MM_WalkHeapStartEvent*)eventData;
+	MM_WalkHeapStartEvent *event = (MM_WalkHeapStartEvent *)eventData;
 	GC_OMRVMInterface::flushCachesForWalk(event->omrVM);
 }
 
 /**
  * Actions required after to walking the heap.
  */
 void
-hookWalkHeapEnd(J9HookInterface** hook, uintptr_t eventNum, void* eventData, void* userData)
+hookWalkHeapEnd(J9HookInterface** hook, uintptr_t eventNum, void *eventData, void *userData)
 {
 	/* Nothing to do right now */
 }
@@ -69,7 +69,7 @@ hookWalkHeapEnd(J9HookInterface** hook, uintptr_t eventNum, void* eventData, voi
 void
 GC_OMRVMInterface::initializeExtensions(MM_GCExtensionsBase *extensions)
 {
-	J9HookInterface** mmPrivateHooks = J9_HOOK_INTERFACE(extensions->privateHookInterface);
+	J9HookInterface **mmPrivateHooks = J9_HOOK_INTERFACE(extensions->privateHookInterface);
 
 	(*mmPrivateHooks)->J9HookRegisterWithCallSite(mmPrivateHooks, J9HOOK_MM_PRIVATE_WALK_HEAP_START, hookWalkHeapStart, OMR_GET_CALLSITE(), NULL);
 	(*mmPrivateHooks)->J9HookRegisterWithCallSite(mmPrivateHooks, J9HOOK_MM_PRIVATE_WALK_HEAP_END, hookWalkHeapEnd, OMR_GET_CALLSITE(), NULL);
@@ -88,19 +88,19 @@ GC_OMRVMInterface::getOmrHookInterface(MM_GCExtensionsBase *extensions)
  * Flush Cache for walk.
  */
 void
-GC_OMRVMInterface::flushCachesForWalk(OMR_VM* omrVM)
+GC_OMRVMInterface::flushCachesForWalk(OMR_VM *omrVM)
 {
 	/*
 	 * Environment at this point might be fake, so we can not get this thread info
 	 * however only one thread suppose to have an exclusive access at this point
 	 */
 	//Assert_MM_true(J9_XACCESS_EXCLUSIVE == vm->exclusiveAccessState);
 
-	OMR_VMThread *omrVMThread;
+	OMR_VMThread *omrVMThread = NULL;
 
 	GC_OMRVMThreadListIterator threadListIterator(omrVM);
 
-	while((omrVMThread = threadListIterator.nextOMRVMThread()) != NULL) {
+	while ((omrVMThread = threadListIterator.nextOMRVMThread()) != NULL) {
 		MM_EnvironmentBase *envToFlush = MM_EnvironmentBase::getEnvironment(omrVMThread);
 		GC_OMRVMThreadInterface::flushCachesForWalk(envToFlush);
 	}
@@ -112,20 +112,28 @@ GC_OMRVMInterface::flushCachesForWalk(OMR_VM* omrVM)
 void
 GC_OMRVMInterface::flushCachesForGC(MM_EnvironmentBase *env)
 {
+	OMRPORT_ACCESS_FROM_ENVIRONMENT(env);
+
 	MM_GCExtensionsBase *extensions = env->getExtensions();
-	OMR_VMThread *omrVMThread;
+	OMR_VMThread *omrVMThread = NULL;
 	UDATA allocatedBytesMax = extensions->bytesAllocatedMost;
 	OMR_VMThread *vmThreadMax = extensions->vmThreadAllocatedMost;
 
+	TRIGGER_J9HOOK_MM_OMR_FLUSH_CACHES_FOR_GC(
+		extensions->omrHookInterface,
+		env->getOmrVMThread(),
+		omrtime_hires_clock(),
+		J9HOOK_MM_OMR_FLUSH_CACHES_FOR_GC);
+
 	GC_OMRVMThreadListIterator threadListIterator(env->getOmrVM());
 
-	while((omrVMThread = threadListIterator.nextOMRVMThread()) != NULL) {
+	while ((omrVMThread = threadListIterator.nextOMRVMThread()) != NULL) {
 		/* Grab allocation bytes stats per-thread before they're cleared */
-		MM_EnvironmentBase* threadEnv = MM_EnvironmentBase::getEnvironment(omrVMThread);
-		MM_AllocationStats * stats= threadEnv->_objectAllocationInterface->getAllocationStats();
+		MM_EnvironmentBase *threadEnv = MM_EnvironmentBase::getEnvironment(omrVMThread);
+		MM_AllocationStats *stats= threadEnv->_objectAllocationInterface->getAllocationStats();
 		UDATA allocatedBytes = stats->bytesAllocated();
 
-		if(allocatedBytes >= allocatedBytesMax){
+		if (allocatedBytes >= allocatedBytesMax){
 			allocatedBytesMax = allocatedBytes;
 			vmThreadMax = omrVMThread;
 		}
@@ -142,11 +150,11 @@ GC_OMRVMInterface::flushCachesForGC(MM_EnvironmentBase *env)
 void
 GC_OMRVMInterface::flushNonAllocationCaches(MM_EnvironmentBase *env)
 {
-	OMR_VMThread *omrVMThread;
+	OMR_VMThread *omrVMThread = NULL;
 
 	GC_OMRVMThreadListIterator threadListIterator(env->getOmrVM());
 
-	while((omrVMThread = threadListIterator.nextOMRVMThread()) != NULL) {
+	while ((omrVMThread = threadListIterator.nextOMRVMThread()) != NULL) {
 		GC_OMRVMThreadInterface::flushNonAllocationCaches(MM_EnvironmentBase::getEnvironment(omrVMThread));
 	}
 }
diff --git a/gc/include/omrmm.hdf b/gc/include/omrmm.hdf
@@ -285,4 +285,17 @@ typedef uintptr_t (*condYieldFromGCFunctionPtr) (OMR_VMThread *omrVMThread, uint
 		<data type="uint64_t" name="timestamp" description="time of event" />
 	</event>
 
+	<event>
+		<name>J9HOOK_MM_OMR_FLUSH_CACHES_FOR_GC</name>
+		<description>
+			This is called slightly after exclusive VM access is acquired, and slightly before various GC start hooks.
+			This is called before flush itself, which deletes all the stats of the various application thread caches.
+			So, it's very similar to the GC start event, except all the stats are still available for reporting and processing.
+		</description>
+		<struct>MM_FlushCachesForGCEvent</struct>
+		<data type="struct OMR_VMThread*" name="currentThread" description="current thread" />
+		<data type="uint64_t" name="timestamp" description="time of event" />
+		<data type="uintptr_t" name="eventid" description="unique identifier for event" />
+	</event>
+
 </interface>