--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/services/mallocSiteTable.cpp Thu Aug 07 12:18:58 2014 -0700
@@ -0,0 +1,261 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+#include "precompiled.hpp"
+
+
+#include "memory/allocation.inline.hpp"
+#include "runtime/atomic.hpp"
+#include "services/mallocSiteTable.hpp"
+
+/*
+ * Early os::malloc() calls come from initializations of static variables, long before entering any
+ * VM code. Upon the arrival of the first os::malloc() call, malloc site hashtable has to be
+ * initialized, along with the allocation site for the hashtable entries.
+ * To ensure that malloc site hashtable can be initialized without triggering any additional os::malloc()
+ * call, the hashtable bucket array and hashtable entry allocation site have to be static.
+ * It is not a problem for hashtable bucket, since it is an array of pointer type, C runtime just
+ * allocates a block memory and zero the memory for it.
+ * But for hashtable entry allocation site object, things get tricky. C runtime not only allocates
+ * memory for it, but also calls its constructor at some later time. If we initialize the allocation site
+ * at the first os::malloc() call, the object will be reinitialized when its constructor is called
+ * by C runtime.
+ * To workaround above issue, we declare a static size_t array with the size of the CallsiteHashtableEntry,
+ * the memory is used to instantiate CallsiteHashtableEntry for the hashtable entry allocation site.
+ * Given it is a primitive type array, C runtime will do nothing other than assign the memory block for the variable,
+ * which is exactly what we want.
+ * The same trick is also applied to create NativeCallStack object for CallsiteHashtableEntry memory allocation.
+ *
+ * Note: C++ object usually aligns to particular alignment, depends on compiler implementation, we declare
+ * the memory as size_t arrays, to ensure the memory is aligned to native machine word alignment.
+ */
+
+// Reserve enough memory for NativeCallStack and MallocSiteHashtableEntry objects
+size_t MallocSiteTable::_hash_entry_allocation_stack[CALC_OBJ_SIZE_IN_TYPE(NativeCallStack, size_t)];
+size_t MallocSiteTable::_hash_entry_allocation_site[CALC_OBJ_SIZE_IN_TYPE(MallocSiteHashtableEntry, size_t)];
+
+// Malloc site hashtable buckets
+MallocSiteHashtableEntry* MallocSiteTable::_table[MallocSiteTable::table_size];
+
+// concurrent access counter
+volatile int MallocSiteTable::_access_count = 0;
+
+// Tracking hashtable contention
+NOT_PRODUCT(int MallocSiteTable::_peak_count = 0;)
+
+
+/*
+ * Initialize malloc site table.
+ * Hashtable entry is malloc'd, so it can cause infinite recursion.
+ * To avoid above problem, we pre-initialize a hash entry for
+ * this allocation site.
+ * The method is called during C runtime static variable initialization
+ * time, it is in single-threaded mode from JVM perspective.
+ */
+bool MallocSiteTable::initialize() {
+ assert(sizeof(_hash_entry_allocation_stack) >= sizeof(NativeCallStack), "Sanity Check");
+ assert(sizeof(_hash_entry_allocation_site) >= sizeof(MallocSiteHashtableEntry),
+ "Sanity Check");
+ assert((size_t)table_size <= MAX_MALLOCSITE_TABLE_SIZE, "Hashtable overflow");
+
+ // Fake the call stack for hashtable entry allocation
+ assert(NMT_TrackingStackDepth > 1, "At least one tracking stack");
+
+ // Create pseudo call stack for hashtable entry allocation
+ address pc[3];
+ if (NMT_TrackingStackDepth >= 3) {
+ pc[2] = (address)MallocSiteTable::allocation_at;
+ }
+ if (NMT_TrackingStackDepth >= 2) {
+ pc[1] = (address)MallocSiteTable::lookup_or_add;
+ }
+ pc[0] = (address)MallocSiteTable::new_entry;
+
+ // Instantiate NativeCallStack object, have to use placement new operator. (see comments above)
+ NativeCallStack* stack = ::new ((void*)_hash_entry_allocation_stack)
+ NativeCallStack(pc, MIN2(((int)(sizeof(pc) / sizeof(address))), ((int)NMT_TrackingStackDepth)));
+
+ // Instantiate hash entry for hashtable entry allocation callsite
+ MallocSiteHashtableEntry* entry = ::new ((void*)_hash_entry_allocation_site)
+ MallocSiteHashtableEntry(*stack);
+
+ // Add the allocation site to hashtable.
+ int index = hash_to_index(stack->hash());
+ _table[index] = entry;
+
+ return true;
+}
+
+// Walks entries in the hashtable.
+// It stops walk if the walker returns false.
+bool MallocSiteTable::walk(MallocSiteWalker* walker) {
+ MallocSiteHashtableEntry* head;
+ for (int index = 0; index < table_size; index ++) {
+ head = _table[index];
+ while (head != NULL) {
+ if (!walker->do_malloc_site(head->peek())) {
+ return false;
+ }
+ head = (MallocSiteHashtableEntry*)head->next();
+ }
+ }
+ return true;
+}
+
+/*
+ * The hashtable does not have deletion policy on individual entry,
+ * and each linked list node is inserted via compare-and-swap,
+ * so each linked list is stable, the contention only happens
+ * at the end of linked list.
+ * This method should not return NULL under normal circumstance.
+ * If NULL is returned, it indicates:
+ * 1. Out of memory, it cannot allocate new hash entry.
+ * 2. Overflow hash bucket.
+ * Under any of above circumstances, caller should handle the situation.
+ */
+MallocSite* MallocSiteTable::lookup_or_add(const NativeCallStack& key, size_t* bucket_idx,
+ size_t* pos_idx) {
+ int index = hash_to_index(key.hash());
+ assert(index >= 0, "Negative index");
+ *bucket_idx = (size_t)index;
+ *pos_idx = 0;
+
+ // First entry for this hash bucket
+ if (_table[index] == NULL) {
+ MallocSiteHashtableEntry* entry = new_entry(key);
+ // OOM check
+ if (entry == NULL) return NULL;
+
+ // swap in the head
+ if (Atomic::cmpxchg_ptr((void*)entry, (volatile void *)&_table[index], NULL) == NULL) {
+ return entry->data();
+ }
+
+ delete entry;
+ }
+
+ MallocSiteHashtableEntry* head = _table[index];
+ while (head != NULL && (*pos_idx) <= MAX_BUCKET_LENGTH) {
+ MallocSite* site = head->data();
+ if (site->equals(key)) {
+ // found matched entry
+ return head->data();
+ }
+
+ if (head->next() == NULL && (*pos_idx) < MAX_BUCKET_LENGTH) {
+ MallocSiteHashtableEntry* entry = new_entry(key);
+ // OOM check
+ if (entry == NULL) return NULL;
+ if (head->atomic_insert(entry)) {
+ (*pos_idx) ++;
+ return entry->data();
+ }
+ // contended, other thread won
+ delete entry;
+ }
+ head = (MallocSiteHashtableEntry*)head->next();
+ (*pos_idx) ++;
+ }
+ return NULL;
+}
+
+// Access malloc site
+MallocSite* MallocSiteTable::malloc_site(size_t bucket_idx, size_t pos_idx) {
+ assert(bucket_idx < table_size, "Invalid bucket index");
+ MallocSiteHashtableEntry* head = _table[bucket_idx];
+ for (size_t index = 0; index < pos_idx && head != NULL;
+ index ++, head = (MallocSiteHashtableEntry*)head->next());
+ assert(head != NULL, "Invalid position index");
+ return head->data();
+}
+
+// Allocates MallocSiteHashtableEntry object. Special call stack
+// (pre-installed allocation site) has to be used to avoid infinite
+// recursion.
+MallocSiteHashtableEntry* MallocSiteTable::new_entry(const NativeCallStack& key) {
+ void* p = AllocateHeap(sizeof(MallocSiteHashtableEntry), mtNMT,
+ *hash_entry_allocation_stack(), AllocFailStrategy::RETURN_NULL);
+ return ::new (p) MallocSiteHashtableEntry(key);
+}
+
+void MallocSiteTable::reset() {
+ for (int index = 0; index < table_size; index ++) {
+ MallocSiteHashtableEntry* head = _table[index];
+ _table[index] = NULL;
+ delete_linked_list(head);
+ }
+}
+
+void MallocSiteTable::delete_linked_list(MallocSiteHashtableEntry* head) {
+ MallocSiteHashtableEntry* p;
+ while (head != NULL) {
+ p = head;
+ head = (MallocSiteHashtableEntry*)head->next();
+ if (p != (MallocSiteHashtableEntry*)_hash_entry_allocation_site) {
+ delete p;
+ }
+ }
+}
+
+void MallocSiteTable::shutdown() {
+ AccessLock locker(&_access_count);
+ locker.exclusiveLock();
+ reset();
+}
+
+bool MallocSiteTable::walk_malloc_site(MallocSiteWalker* walker) {
+ assert(walker != NULL, "NuLL walker");
+ AccessLock locker(&_access_count);
+ if (locker.sharedLock()) {
+ NOT_PRODUCT(_peak_count = MAX2(_peak_count, _access_count);)
+ return walk(walker);
+ }
+ return false;
+}
+
+
+void MallocSiteTable::AccessLock::exclusiveLock() {
+ jint target;
+ jint val;
+
+ assert(_lock_state != ExclusiveLock, "Can only call once");
+ assert(*_lock >= 0, "Can not content exclusive lock");
+
+ // make counter negative to block out shared locks
+ do {
+ val = *_lock;
+ target = _MAGIC_ + *_lock;
+ } while (Atomic::cmpxchg(target, _lock, val) != val);
+
+ // wait for all readers to exit
+ while (*_lock != _MAGIC_) {
+#ifdef _WINDOWS
+ os::naked_short_sleep(1);
+#else
+ os::naked_yield();
+#endif
+ }
+ _lock_state = ExclusiveLock;
+}
+
+