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20360
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1 /*
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2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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20 * or visit www.oracle.com if you need additional information or have any
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21 * questions.
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22 *
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23 */
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24 #include "precompiled.hpp"
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25
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26
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27 #include "memory/allocation.inline.hpp"
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28 #include "runtime/atomic.hpp"
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29 #include "services/mallocSiteTable.hpp"
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30
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31 /*
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32 * Early os::malloc() calls come from initializations of static variables, long before entering any
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33 * VM code. Upon the arrival of the first os::malloc() call, malloc site hashtable has to be
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34 * initialized, along with the allocation site for the hashtable entries.
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35 * To ensure that malloc site hashtable can be initialized without triggering any additional os::malloc()
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36 * call, the hashtable bucket array and hashtable entry allocation site have to be static.
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37 * It is not a problem for hashtable bucket, since it is an array of pointer type, C runtime just
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38 * allocates a block memory and zero the memory for it.
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39 * But for hashtable entry allocation site object, things get tricky. C runtime not only allocates
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40 * memory for it, but also calls its constructor at some later time. If we initialize the allocation site
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41 * at the first os::malloc() call, the object will be reinitialized when its constructor is called
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42 * by C runtime.
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43 * To workaround above issue, we declare a static size_t array with the size of the CallsiteHashtableEntry,
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44 * the memory is used to instantiate CallsiteHashtableEntry for the hashtable entry allocation site.
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45 * Given it is a primitive type array, C runtime will do nothing other than assign the memory block for the variable,
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46 * which is exactly what we want.
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47 * The same trick is also applied to create NativeCallStack object for CallsiteHashtableEntry memory allocation.
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48 *
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49 * Note: C++ object usually aligns to particular alignment, depends on compiler implementation, we declare
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50 * the memory as size_t arrays, to ensure the memory is aligned to native machine word alignment.
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51 */
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52
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53 // Reserve enough memory for NativeCallStack and MallocSiteHashtableEntry objects
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54 size_t MallocSiteTable::_hash_entry_allocation_stack[CALC_OBJ_SIZE_IN_TYPE(NativeCallStack, size_t)];
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55 size_t MallocSiteTable::_hash_entry_allocation_site[CALC_OBJ_SIZE_IN_TYPE(MallocSiteHashtableEntry, size_t)];
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56
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57 // Malloc site hashtable buckets
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58 MallocSiteHashtableEntry* MallocSiteTable::_table[MallocSiteTable::table_size];
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59
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60 // concurrent access counter
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61 volatile int MallocSiteTable::_access_count = 0;
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62
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63 // Tracking hashtable contention
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64 NOT_PRODUCT(int MallocSiteTable::_peak_count = 0;)
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65
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66
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67 /*
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68 * Initialize malloc site table.
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69 * Hashtable entry is malloc'd, so it can cause infinite recursion.
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70 * To avoid above problem, we pre-initialize a hash entry for
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71 * this allocation site.
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72 * The method is called during C runtime static variable initialization
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73 * time, it is in single-threaded mode from JVM perspective.
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74 */
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75 bool MallocSiteTable::initialize() {
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76 assert(sizeof(_hash_entry_allocation_stack) >= sizeof(NativeCallStack), "Sanity Check");
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77 assert(sizeof(_hash_entry_allocation_site) >= sizeof(MallocSiteHashtableEntry),
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78 "Sanity Check");
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79 assert((size_t)table_size <= MAX_MALLOCSITE_TABLE_SIZE, "Hashtable overflow");
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80
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81 // Fake the call stack for hashtable entry allocation
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82 assert(NMT_TrackingStackDepth > 1, "At least one tracking stack");
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83
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84 // Create pseudo call stack for hashtable entry allocation
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85 address pc[3];
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86 if (NMT_TrackingStackDepth >= 3) {
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87 pc[2] = (address)MallocSiteTable::allocation_at;
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88 }
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89 if (NMT_TrackingStackDepth >= 2) {
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90 pc[1] = (address)MallocSiteTable::lookup_or_add;
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91 }
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92 pc[0] = (address)MallocSiteTable::new_entry;
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93
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94 // Instantiate NativeCallStack object, have to use placement new operator. (see comments above)
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95 NativeCallStack* stack = ::new ((void*)_hash_entry_allocation_stack)
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96 NativeCallStack(pc, MIN2(((int)(sizeof(pc) / sizeof(address))), ((int)NMT_TrackingStackDepth)));
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97
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98 // Instantiate hash entry for hashtable entry allocation callsite
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99 MallocSiteHashtableEntry* entry = ::new ((void*)_hash_entry_allocation_site)
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100 MallocSiteHashtableEntry(*stack);
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101
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102 // Add the allocation site to hashtable.
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103 int index = hash_to_index(stack->hash());
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104 _table[index] = entry;
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105
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106 return true;
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107 }
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108
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109 // Walks entries in the hashtable.
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110 // It stops walk if the walker returns false.
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111 bool MallocSiteTable::walk(MallocSiteWalker* walker) {
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112 MallocSiteHashtableEntry* head;
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113 for (int index = 0; index < table_size; index ++) {
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114 head = _table[index];
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115 while (head != NULL) {
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116 if (!walker->do_malloc_site(head->peek())) {
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117 return false;
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118 }
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119 head = (MallocSiteHashtableEntry*)head->next();
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120 }
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121 }
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122 return true;
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123 }
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124
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125 /*
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126 * The hashtable does not have deletion policy on individual entry,
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127 * and each linked list node is inserted via compare-and-swap,
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128 * so each linked list is stable, the contention only happens
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129 * at the end of linked list.
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130 * This method should not return NULL under normal circumstance.
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131 * If NULL is returned, it indicates:
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132 * 1. Out of memory, it cannot allocate new hash entry.
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133 * 2. Overflow hash bucket.
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134 * Under any of above circumstances, caller should handle the situation.
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135 */
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136 MallocSite* MallocSiteTable::lookup_or_add(const NativeCallStack& key, size_t* bucket_idx,
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137 size_t* pos_idx) {
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138 int index = hash_to_index(key.hash());
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139 assert(index >= 0, "Negative index");
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140 *bucket_idx = (size_t)index;
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141 *pos_idx = 0;
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142
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143 // First entry for this hash bucket
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144 if (_table[index] == NULL) {
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145 MallocSiteHashtableEntry* entry = new_entry(key);
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146 // OOM check
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147 if (entry == NULL) return NULL;
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148
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149 // swap in the head
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150 if (Atomic::cmpxchg_ptr((void*)entry, (volatile void *)&_table[index], NULL) == NULL) {
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151 return entry->data();
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152 }
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153
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154 delete entry;
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155 }
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156
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157 MallocSiteHashtableEntry* head = _table[index];
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158 while (head != NULL && (*pos_idx) <= MAX_BUCKET_LENGTH) {
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159 MallocSite* site = head->data();
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160 if (site->equals(key)) {
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161 // found matched entry
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162 return head->data();
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163 }
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164
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165 if (head->next() == NULL && (*pos_idx) < MAX_BUCKET_LENGTH) {
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166 MallocSiteHashtableEntry* entry = new_entry(key);
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167 // OOM check
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168 if (entry == NULL) return NULL;
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169 if (head->atomic_insert(entry)) {
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170 (*pos_idx) ++;
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171 return entry->data();
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172 }
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173 // contended, other thread won
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174 delete entry;
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175 }
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176 head = (MallocSiteHashtableEntry*)head->next();
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177 (*pos_idx) ++;
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178 }
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179 return NULL;
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180 }
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181
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182 // Access malloc site
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183 MallocSite* MallocSiteTable::malloc_site(size_t bucket_idx, size_t pos_idx) {
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184 assert(bucket_idx < table_size, "Invalid bucket index");
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185 MallocSiteHashtableEntry* head = _table[bucket_idx];
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186 for (size_t index = 0; index < pos_idx && head != NULL;
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187 index ++, head = (MallocSiteHashtableEntry*)head->next());
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188 assert(head != NULL, "Invalid position index");
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189 return head->data();
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190 }
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191
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192 // Allocates MallocSiteHashtableEntry object. Special call stack
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193 // (pre-installed allocation site) has to be used to avoid infinite
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194 // recursion.
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195 MallocSiteHashtableEntry* MallocSiteTable::new_entry(const NativeCallStack& key) {
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196 void* p = AllocateHeap(sizeof(MallocSiteHashtableEntry), mtNMT,
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197 *hash_entry_allocation_stack(), AllocFailStrategy::RETURN_NULL);
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198 return ::new (p) MallocSiteHashtableEntry(key);
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199 }
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200
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201 void MallocSiteTable::reset() {
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202 for (int index = 0; index < table_size; index ++) {
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203 MallocSiteHashtableEntry* head = _table[index];
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204 _table[index] = NULL;
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205 delete_linked_list(head);
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206 }
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207 }
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208
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209 void MallocSiteTable::delete_linked_list(MallocSiteHashtableEntry* head) {
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210 MallocSiteHashtableEntry* p;
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211 while (head != NULL) {
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212 p = head;
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213 head = (MallocSiteHashtableEntry*)head->next();
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214 if (p != (MallocSiteHashtableEntry*)_hash_entry_allocation_site) {
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215 delete p;
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216 }
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217 }
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218 }
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219
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220 void MallocSiteTable::shutdown() {
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221 AccessLock locker(&_access_count);
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222 locker.exclusiveLock();
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223 reset();
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224 }
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225
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226 bool MallocSiteTable::walk_malloc_site(MallocSiteWalker* walker) {
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227 assert(walker != NULL, "NuLL walker");
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228 AccessLock locker(&_access_count);
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229 if (locker.sharedLock()) {
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230 NOT_PRODUCT(_peak_count = MAX2(_peak_count, _access_count);)
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231 return walk(walker);
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232 }
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233 return false;
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234 }
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235
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236
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237 void MallocSiteTable::AccessLock::exclusiveLock() {
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238 jint target;
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239 jint val;
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240
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241 assert(_lock_state != ExclusiveLock, "Can only call once");
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242 assert(*_lock >= 0, "Can not content exclusive lock");
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243
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244 // make counter negative to block out shared locks
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245 do {
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246 val = *_lock;
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247 target = _MAGIC_ + *_lock;
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248 } while (Atomic::cmpxchg(target, _lock, val) != val);
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249
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250 // wait for all readers to exit
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251 while (*_lock != _MAGIC_) {
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252 #ifdef _WINDOWS
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253 os::naked_short_sleep(1);
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254 #else
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255 os::NakedYield();
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256 #endif
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257 }
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258 _lock_state = ExclusiveLock;
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259 }
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260
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261
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