1/*
2 * Copyright (c) 2014, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24#include "precompiled.hpp"
25
26
27#include "memory/allocation.inline.hpp"
28#include "runtime/atomic.hpp"
29#include "services/mallocSiteTable.hpp"
30
31/*
32 * Early os::malloc() calls come from initializations of static variables, long before entering any
33 * VM code. Upon the arrival of the first os::malloc() call, malloc site hashtable has to be
34 * initialized, along with the allocation site for the hashtable entries.
35 * To ensure that malloc site hashtable can be initialized without triggering any additional os::malloc()
36 * call, the hashtable bucket array and hashtable entry allocation site have to be static.
37 * It is not a problem for hashtable bucket, since it is an array of pointer type, C runtime just
38 * allocates a block memory and zero the memory for it.
39 * But for hashtable entry allocation site object, things get tricky. C runtime not only allocates
40 * memory for it, but also calls its constructor at some later time. If we initialize the allocation site
41 * at the first os::malloc() call, the object will be reinitialized when its constructor is called
42 * by C runtime.
43 * To workaround above issue, we declare a static size_t array with the size of the CallsiteHashtableEntry,
44 * the memory is used to instantiate CallsiteHashtableEntry for the hashtable entry allocation site.
45 * Given it is a primitive type array, C runtime will do nothing other than assign the memory block for the variable,
46 * which is exactly what we want.
47 * The same trick is also applied to create NativeCallStack object for CallsiteHashtableEntry memory allocation.
48 *
49 * Note: C++ object usually aligns to particular alignment, depends on compiler implementation, we declare
50 * the memory as size_t arrays, to ensure the memory is aligned to native machine word alignment.
51 */
52
53// Reserve enough memory for NativeCallStack and MallocSiteHashtableEntry objects
54size_t MallocSiteTable::_hash_entry_allocation_stack[CALC_OBJ_SIZE_IN_TYPE(NativeCallStack, size_t)];
55size_t MallocSiteTable::_hash_entry_allocation_site[CALC_OBJ_SIZE_IN_TYPE(MallocSiteHashtableEntry, size_t)];
56
57// Malloc site hashtable buckets
58MallocSiteHashtableEntry*  MallocSiteTable::_table[MallocSiteTable::table_size];
59
60// concurrent access counter
61volatile int MallocSiteTable::_access_count = 0;
62
63// Tracking hashtable contention
64NOT_PRODUCT(int MallocSiteTable::_peak_count = 0;)
65
66
67/*
68 * Initialize malloc site table.
69 * Hashtable entry is malloc'd, so it can cause infinite recursion.
70 * To avoid above problem, we pre-initialize a hash entry for
71 * this allocation site.
72 * The method is called during C runtime static variable initialization
73 * time, it is in single-threaded mode from JVM perspective.
74 */
75bool MallocSiteTable::initialize() {
76  assert(sizeof(_hash_entry_allocation_stack) >= sizeof(NativeCallStack), "Sanity Check");
77  assert(sizeof(_hash_entry_allocation_site) >= sizeof(MallocSiteHashtableEntry),
78    "Sanity Check");
79  assert((size_t)table_size <= MAX_MALLOCSITE_TABLE_SIZE, "Hashtable overflow");
80
81  // Fake the call stack for hashtable entry allocation
82  assert(NMT_TrackingStackDepth > 1, "At least one tracking stack");
83
84  // Create pseudo call stack for hashtable entry allocation
85  address pc[3];
86  if (NMT_TrackingStackDepth >= 3) {
87    pc[2] = (address)MallocSiteTable::allocation_at;
88  }
89  if (NMT_TrackingStackDepth >= 2) {
90    pc[1] = (address)MallocSiteTable::lookup_or_add;
91  }
92  pc[0] = (address)MallocSiteTable::new_entry;
93
94  // Instantiate NativeCallStack object, have to use placement new operator. (see comments above)
95  NativeCallStack* stack = ::new ((void*)_hash_entry_allocation_stack)
96    NativeCallStack(pc, MIN2(((int)(sizeof(pc) / sizeof(address))), ((int)NMT_TrackingStackDepth)));
97
98  // Instantiate hash entry for hashtable entry allocation callsite
99  MallocSiteHashtableEntry* entry = ::new ((void*)_hash_entry_allocation_site)
100    MallocSiteHashtableEntry(*stack, mtNMT);
101
102  // Add the allocation site to hashtable.
103  int index = hash_to_index(stack->hash());
104  _table[index] = entry;
105
106  return true;
107}
108
109// Walks entries in the hashtable.
110// It stops walk if the walker returns false.
111bool MallocSiteTable::walk(MallocSiteWalker* walker) {
112  MallocSiteHashtableEntry* head;
113  for (int index = 0; index < table_size; index ++) {
114    head = _table[index];
115    while (head != NULL) {
116      if (!walker->do_malloc_site(head->peek())) {
117        return false;
118      }
119      head = (MallocSiteHashtableEntry*)head->next();
120    }
121  }
122  return true;
123}
124
125/*
126 *  The hashtable does not have deletion policy on individual entry,
127 *  and each linked list node is inserted via compare-and-swap,
128 *  so each linked list is stable, the contention only happens
129 *  at the end of linked list.
130 *  This method should not return NULL under normal circumstance.
131 *  If NULL is returned, it indicates:
132 *    1. Out of memory, it cannot allocate new hash entry.
133 *    2. Overflow hash bucket.
134 *  Under any of above circumstances, caller should handle the situation.
135 */
136MallocSite* MallocSiteTable::lookup_or_add(const NativeCallStack& key, size_t* bucket_idx,
137  size_t* pos_idx, MEMFLAGS flags) {
138  assert(flags != mtNone, "Should have a real memory type");
139  unsigned int index = hash_to_index(key.hash());
140  *bucket_idx = (size_t)index;
141  *pos_idx = 0;
142
143  // First entry for this hash bucket
144  if (_table[index] == NULL) {
145    MallocSiteHashtableEntry* entry = new_entry(key, flags);
146    // OOM check
147    if (entry == NULL) return NULL;
148
149    // swap in the head
150    if (Atomic::cmpxchg_ptr((void*)entry, (volatile void *)&_table[index], NULL) == NULL) {
151      return entry->data();
152    }
153
154    delete entry;
155  }
156
157  MallocSiteHashtableEntry* head = _table[index];
158  while (head != NULL && (*pos_idx) <= MAX_BUCKET_LENGTH) {
159    MallocSite* site = head->data();
160    if (site->flags() == flags && site->equals(key)) {
161      return head->data();
162    }
163
164    if (head->next() == NULL && (*pos_idx) < MAX_BUCKET_LENGTH) {
165      MallocSiteHashtableEntry* entry = new_entry(key, flags);
166      // OOM check
167      if (entry == NULL) return NULL;
168      if (head->atomic_insert(entry)) {
169        (*pos_idx) ++;
170        return entry->data();
171      }
172      // contended, other thread won
173      delete entry;
174    }
175    head = (MallocSiteHashtableEntry*)head->next();
176    (*pos_idx) ++;
177  }
178  return NULL;
179}
180
181// Access malloc site
182MallocSite* MallocSiteTable::malloc_site(size_t bucket_idx, size_t pos_idx) {
183  assert(bucket_idx < table_size, "Invalid bucket index");
184  MallocSiteHashtableEntry* head = _table[bucket_idx];
185  for (size_t index = 0;
186       index < pos_idx && head != NULL;
187       index++, head = (MallocSiteHashtableEntry*)head->next()) {}
188  assert(head != NULL, "Invalid position index");
189  return head->data();
190}
191
192// Allocates MallocSiteHashtableEntry object. Special call stack
193// (pre-installed allocation site) has to be used to avoid infinite
194// recursion.
195MallocSiteHashtableEntry* MallocSiteTable::new_entry(const NativeCallStack& key, MEMFLAGS flags) {
196  void* p = AllocateHeap(sizeof(MallocSiteHashtableEntry), mtNMT,
197    *hash_entry_allocation_stack(), AllocFailStrategy::RETURN_NULL);
198  return ::new (p) MallocSiteHashtableEntry(key, flags);
199}
200
201void MallocSiteTable::reset() {
202  for (int index = 0; index < table_size; index ++) {
203    MallocSiteHashtableEntry* head = _table[index];
204    _table[index] = NULL;
205    delete_linked_list(head);
206  }
207}
208
209void MallocSiteTable::delete_linked_list(MallocSiteHashtableEntry* head) {
210  MallocSiteHashtableEntry* p;
211  while (head != NULL) {
212    p = head;
213    head = (MallocSiteHashtableEntry*)head->next();
214    if (p != (MallocSiteHashtableEntry*)_hash_entry_allocation_site) {
215      delete p;
216    }
217  }
218}
219
220void MallocSiteTable::shutdown() {
221  AccessLock locker(&_access_count);
222  locker.exclusiveLock();
223  reset();
224}
225
226bool MallocSiteTable::walk_malloc_site(MallocSiteWalker* walker) {
227  assert(walker != NULL, "NuLL walker");
228  AccessLock locker(&_access_count);
229  if (locker.sharedLock()) {
230    NOT_PRODUCT(_peak_count = MAX2(_peak_count, _access_count);)
231    return walk(walker);
232  }
233  return false;
234}
235
236
237void MallocSiteTable::AccessLock::exclusiveLock() {
238  jint target;
239  jint val;
240
241  assert(_lock_state != ExclusiveLock, "Can only call once");
242  assert(*_lock >= 0, "Can not content exclusive lock");
243
244  // make counter negative to block out shared locks
245  do {
246    val = *_lock;
247    target = _MAGIC_ + *_lock;
248  } while (Atomic::cmpxchg(target, _lock, val) != val);
249
250  // wait for all readers to exit
251  while (*_lock != _MAGIC_) {
252#ifdef _WINDOWS
253    os::naked_short_sleep(1);
254#else
255    os::naked_yield();
256#endif
257  }
258  _lock_state = ExclusiveLock;
259}
260