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
54 size_t MallocSiteTable::_hash_entry_allocation_stack[CALC_OBJ_SIZE_IN_TYPE(NativeCallStack, size_t)];
55 size_t MallocSiteTable::_hash_entry_allocation_site[CALC_OBJ_SIZE_IN_TYPE(MallocSiteHashtableEntry, size_t)];
56
57 // Malloc site hashtable buckets
58 MallocSiteHashtableEntry* MallocSiteTable::_table[MallocSiteTable::table_size];
59
60 // concurrent access counter
61 volatile int MallocSiteTable::_access_count = 0;
62
63 // Tracking hashtable contention
64 NOT_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 */
75 bool 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.
111 bool 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 */
136 MallocSite* 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
182 MallocSite* 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.
195 MallocSiteHashtableEntry* 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
201 void 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
209 void 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
220 void MallocSiteTable::shutdown() {
221 AccessLock locker(&_access_count);
222 locker.exclusiveLock();
223 reset();
224 }
225
226 bool 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
237 void 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 }