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src/jdk.jdwp.agent/share/native/libjdwp/classTrack.c
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rev 57742 : 8227269: Slow class loading when running with JDWP
@@ -43,252 +43,275 @@
#include "util.h"
#include "bag.h"
#include "classTrack.h"
-/* ClassTrack hash table slot count */
-#define CT_HASH_SLOT_COUNT 263 /* Prime which eauals 4k+3 for some k */
+/* ClassTrack table slot count */
+#define CT_SLOT_COUNT 263 /* Prime which eauals 4k+3 for some k */
typedef struct KlassNode {
- jclass klass; /* weak global reference */
+ jlong klass_tag; /* Klass's tag in tracking env */
char *signature; /* class signature */
struct KlassNode *next; /* next node in this slot */
} KlassNode;
/*
- * Hash table of prepared classes. Each entry is a pointer
- * to a linked list of KlassNode.
+ * Table mapping tag % CT_SLOT_COUNT to linked-list of KlassNode*.
*/
-static KlassNode **table;
+static KlassNode** table;
/*
- * Return slot in hash table to use for this class.
+ * The JVMTI tracking env to keep track of klass tags, for class-unloads
*/
-static jint
-hashKlass(jclass klass)
-{
- jint hashCode = objectHashCode(klass);
- return abs(hashCode) % CT_HASH_SLOT_COUNT;
-}
+static jvmtiEnv* trackingEnv;
/*
- * Transfer a node (which represents klass) from the current
- * table to the new table.
+ * The current highest tag number
*/
-static void
-transferClass(JNIEnv *env, jclass klass, KlassNode **newTable) {
- jint slot = hashKlass(klass);
- KlassNode **head = &table[slot];
- KlassNode **newHead = &newTable[slot];
- KlassNode **nodePtr;
- KlassNode *node;
-
- /* Search the node list of the current table for klass */
- for (nodePtr = head; node = *nodePtr, node != NULL; nodePtr = &(node->next)) {
- if (isSameObject(env, klass, node->klass)) {
- /* Match found transfer node */
+static jlong currentClassTag;
- /* unlink from old list */
- *nodePtr = node->next;
-
- /* insert in new list */
- node->next = *newHead;
- *newHead = node;
-
- return;
- }
- }
+/*
+ * Lock to keep table, currentClassTag and deletedSignatureBag consistent
+ */
+static jrawMonitorID deletedSignatureLock;
- /* we haven't found the class, only unloads should have happenned,
- * so the only reason a class should not have been found is
- * that it is not prepared yet, in which case we don't want it.
- * Asset that the above is true.
+/*
+ * A bag containing all the deleted classes' signatures. Must be accessed under
+ * deletedSignatureLock.
*/
-/**** the HotSpot VM doesn't create prepare events for some internal classes ***
- JDI_ASSERT_MSG((classStatus(klass) &
- (JVMTI_CLASS_STATUS_PREPARED|JVMTI_CLASS_STATUS_ARRAY))==0,
- classSignature(klass));
-***/
-}
+struct bag* deletedSignatureBag;
/*
- * Delete a hash table of classes.
- * The signatures of classes in the table are returned.
+ * Callback when classes are freed, Finds the signature and remembers it in deletedSignatureBag.
*/
-static struct bag *
-deleteTable(JNIEnv *env, KlassNode *oldTable[])
+static void JNICALL
+cbTrackingObjectFree(jvmtiEnv* jvmti_env, jlong tag)
{
- struct bag *signatures = bagCreateBag(sizeof(char*), 10);
- jint slot;
-
- if (signatures == NULL) {
- EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"signatures");
+ debugMonitorEnter(deletedSignatureLock);
+ if (currentClassTag == -1) {
+ // Class tracking not initialized, nobody's interested
+ debugMonitorExit(deletedSignatureLock);
+ return;
}
- for (slot = 0; slot < CT_HASH_SLOT_COUNT; slot++) {
- KlassNode *node = oldTable[slot];
-
- while (node != NULL) {
- KlassNode *next;
- char **sigSpot;
-
- /* Add signature to the signature bag */
- sigSpot = bagAdd(signatures);
- if (sigSpot == NULL) {
- EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"signature bag");
- }
- *sigSpot = node->signature;
-
- /* Free weak ref and the node itself */
- JNI_FUNC_PTR(env,DeleteWeakGlobalRef)(env, node->klass);
- next = node->next;
- jvmtiDeallocate(node);
-
- node = next;
+ // Find deleted KlassNode
+ size_t idx = tag % CT_SLOT_COUNT;
+ KlassNode** klass_ptr = &table[idx];
+ KlassNode* klass = *klass_ptr;
+
+ // Scan linked-list.
+ while (klass != NULL && klass->klass_tag != tag) {
+ klass_ptr = &klass->next;
+ klass = *klass_ptr;
}
+ if (klass != NULL || klass->klass_tag != tag) { // klass not found - ignore.
+ debugMonitorExit(deletedSignatureLock);
+ return;
}
- jvmtiDeallocate(oldTable);
- return signatures;
+ // At this point we have the KlassNode corresponding to the tag
+ // in klass, and the pointer to it in klass_node.
+ // Remember the unloaded signature.
+ *(char**)bagAdd(deletedSignatureBag) = klass->signature;
+
+ // Unlink the KlassNode.
+ *klass_ptr = klass->next;
+ jvmtiDeallocate(klass);
+
+ // Done.
+ debugMonitorExit(deletedSignatureLock);
}
/*
- * Called after class unloads have occurred. Creates a new hash table
- * of currently loaded prepared classes.
- * The signatures of classes which were unloaded (not present in the
- * new table) are returned.
+ * Called after class unloads have occurred.
+ * The signatures of classes which were unloaded are returned.
*/
struct bag *
classTrack_processUnloads(JNIEnv *env)
{
- KlassNode **newTable;
- struct bag *unloadedSignatures;
-
- unloadedSignatures = NULL;
- newTable = jvmtiAllocate(CT_HASH_SLOT_COUNT * sizeof(KlassNode *));
- if (newTable == NULL) {
- EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY, "classTrack table");
- } else {
-
- (void)memset(newTable, 0, CT_HASH_SLOT_COUNT * sizeof(KlassNode *));
-
- WITH_LOCAL_REFS(env, 1) {
-
- jint classCount;
- jclass *classes;
- jvmtiError error;
- int i;
-
- error = allLoadedClasses(&classes, &classCount);
- if ( error != JVMTI_ERROR_NONE ) {
- jvmtiDeallocate(newTable);
- EXIT_ERROR(error,"loaded classes");
- } else {
-
- /* Transfer each current class into the new table */
- for (i=0; i<classCount; i++) {
- jclass klass = classes[i];
- transferClass(env, klass, newTable);
- }
- jvmtiDeallocate(classes);
-
- /* Delete old table, install new one */
- unloadedSignatures = deleteTable(env, table);
- table = newTable;
- }
-
- } END_WITH_LOCAL_REFS(env)
-
- }
-
- return unloadedSignatures;
+ debugMonitorEnter(deletedSignatureLock);
+ if (currentClassTag == -1) {
+ // Class tracking not initialized, nobody's interested
+ debugMonitorExit(deletedSignatureLock);
+ return bagCreateBag(sizeof(char*), 0);
+ }
+ struct bag* deleted = deletedSignatureBag;
+ deletedSignatureBag = bagCreateBag(sizeof(char*), 10);
+ debugMonitorExit(deletedSignatureLock);
+ return deleted;
}
/*
- * Add a class to the prepared class hash table.
- * Assumes no duplicates.
+ * Add a class to the prepared class table.
*/
void
classTrack_addPreparedClass(JNIEnv *env, jclass klass)
{
- jint slot = hashKlass(klass);
- KlassNode **head = &table[slot];
- KlassNode *node;
jvmtiError error;
- if (gdata->assertOn) {
- /* Check this is not a duplicate */
- for (node = *head; node != NULL; node = node->next) {
- if (isSameObject(env, klass, node->klass)) {
- JDI_ASSERT_FAILED("Attempting to insert duplicate class");
- break;
+ debugMonitorEnter(deletedSignatureLock);
+ if (currentClassTag == -1) {
+ // Class tracking not initialized yet, nobody's interested
+ debugMonitorExit(deletedSignatureLock);
+ return;
}
+
+ /* Check this is not a duplicate */
+ jlong tag;
+ error = JVMTI_FUNC_PTR(trackingEnv, GetTag)(trackingEnv, klass, &tag);
+ if (error != JVMTI_ERROR_NONE) {
+ EXIT_ERROR(error, "Unable to GetTag with class trackingEnv");
}
+ if (tag != 0l) {
+ debugMonitorExit(deletedSignatureLock);
+ return; // Already added
}
- node = jvmtiAllocate(sizeof(KlassNode));
+ KlassNode* node = jvmtiAllocate(sizeof(KlassNode));
if (node == NULL) {
EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"KlassNode");
}
error = classSignature(klass, &(node->signature), NULL);
if (error != JVMTI_ERROR_NONE) {
jvmtiDeallocate(node);
EXIT_ERROR(error,"signature");
}
- if ((node->klass = JNI_FUNC_PTR(env,NewWeakGlobalRef)(env, klass)) == NULL) {
+ node->klass_tag = ++currentClassTag;
+ error = JVMTI_FUNC_PTR(trackingEnv, SetTag)(trackingEnv, klass, node->klass_tag);
+ if (error != JVMTI_ERROR_NONE) {
jvmtiDeallocate(node->signature);
jvmtiDeallocate(node);
- EXIT_ERROR(AGENT_ERROR_NULL_POINTER,"NewWeakGlobalRef");
+ EXIT_ERROR(error,"SetTag");
}
/* Insert the new node */
- node->next = *head;
- *head = node;
+ size_t idx = node->klass_tag % CT_SLOT_COUNT;
+ node->next = table[idx];
+ table[idx] = node;
+ debugMonitorExit(deletedSignatureLock);
+}
+
+static jboolean
+setupEvents()
+{
+ jvmtiCapabilities caps;
+ memset(&caps, 0, sizeof(caps));
+ caps.can_generate_object_free_events = 1;
+ jvmtiError error = JVMTI_FUNC_PTR(trackingEnv, AddCapabilities)(trackingEnv, &caps);
+ if (error != JVMTI_ERROR_NONE) {
+ return JNI_FALSE;
+ }
+ jvmtiEventCallbacks cb;
+ memset(&cb, 0, sizeof(cb));
+ cb.ObjectFree = cbTrackingObjectFree;
+ error = JVMTI_FUNC_PTR(trackingEnv, SetEventCallbacks)(trackingEnv, &cb, sizeof(cb));
+ if (error != JVMTI_ERROR_NONE) {
+ return JNI_FALSE;
+ }
+ error = JVMTI_FUNC_PTR(trackingEnv, SetEventNotificationMode)(trackingEnv, JVMTI_ENABLE, JVMTI_EVENT_OBJECT_FREE, NULL);
+ if (error != JVMTI_ERROR_NONE) {
+ return JNI_FALSE;
+ }
+ return JNI_TRUE;
}
/*
- * Called once to build the initial prepared class hash table.
+ * Called once to initialize class-tracking.
*/
void
classTrack_initialize(JNIEnv *env)
{
+ deletedSignatureLock = debugMonitorCreate("Deleted class tag lock");
+ currentClassTag = -1l;
+ table = NULL;
+ trackingEnv = NULL;
+ deletedSignatureBag = NULL;
+}
+
+/*
+ * Called to activate class-tracking when a listener registers for EI_GC_FINISH.
+ */
+void
+classTrack_activate(JNIEnv *env)
+{
+ trackingEnv = getSpecialJvmti();
+ if (trackingEnv == NULL) {
+ EXIT_ERROR(AGENT_ERROR_INTERNAL, "Failed to allocate tag-tracking jvmtiEnv");
+ }
+
+ deletedSignatureBag = bagCreateBag(sizeof(char*), 10);
+
+ if (!setupEvents()) {
+ EXIT_ERROR(AGENT_ERROR_INTERNAL, "Unable to setup ObjectFree tracking");
+ }
+ currentClassTag = 0l;
+ table = jvmtiAllocate(CT_SLOT_COUNT * sizeof(KlassNode*));
+ if (table != NULL) {
+ (void)memset(table, 0, CT_SLOT_COUNT * sizeof(KlassNode*));
+ } else {
+ EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY, "failed allocating class-track table");
+ }
+
WITH_LOCAL_REFS(env, 1) {
jint classCount;
jclass *classes;
jvmtiError error;
jint i;
error = allLoadedClasses(&classes, &classCount);
if ( error == JVMTI_ERROR_NONE ) {
- table = jvmtiAllocate(CT_HASH_SLOT_COUNT * sizeof(KlassNode *));
- if (table != NULL) {
- (void)memset(table, 0, CT_HASH_SLOT_COUNT * sizeof(KlassNode *));
- for (i=0; i<classCount; i++) {
+ for (i = 0; i < classCount; i++) {
jclass klass = classes[i];
jint status;
- jint wanted =
- (JVMTI_CLASS_STATUS_PREPARED|JVMTI_CLASS_STATUS_ARRAY);
-
- /* We only want prepared classes and arrays */
+ jint wanted = JVMTI_CLASS_STATUS_PREPARED | JVMTI_CLASS_STATUS_ARRAY;
status = classStatus(klass);
- if ( (status & wanted) != 0 ) {
+ if ((status & wanted) != 0) {
classTrack_addPreparedClass(env, klass);
}
}
- } else {
- jvmtiDeallocate(classes);
- EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"KlassNode");
- }
jvmtiDeallocate(classes);
} else {
EXIT_ERROR(error,"loaded classes array");
}
} END_WITH_LOCAL_REFS(env)
+}
+static jboolean
+cleanDeleted(void *signatureVoid, void *arg)
+{
+ char* sig = (char*)signatureVoid;
+ jvmtiDeallocate(sig);
+ return JNI_TRUE;
}
+/*
+ * Called when agent detaches.
+ */
void
classTrack_reset(void)
{
+ int idx;
+ debugMonitorEnter(deletedSignatureLock);
+
+ for (idx = 0; idx < CT_SLOT_COUNT; ++idx) {
+ KlassNode* node = table[idx];
+ while (node != NULL) {
+ KlassNode* next = node->next;
+ jvmtiDeallocate(node->signature);
+ jvmtiDeallocate(node);
+ node = next;
+ }
+ }
+ jvmtiDeallocate(table);
+
+ bagEnumerateOver(deletedSignatureBag, cleanDeleted, NULL);
+ bagDestroyBag(deletedSignatureBag);
+
+ currentClassTag = -1;
+
+ (void)JVMTI_FUNC_PTR(trackingEnv,DisposeEnvironment)(trackingEnv);
+ trackingEnv = NULL;
+
+ debugMonitorExit(deletedSignatureLock);
}
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