0
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1 /* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
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2 /*
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3 * Thread management for memcached.
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4 *
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5 * $Id$
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6 */
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7 #include "memcached.h"
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8 #include <stdio.h>
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9 #include <errno.h>
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10 #include <stdlib.h>
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11 #include <errno.h>
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12
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13 #ifdef HAVE_MALLOC_H
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14 #include <malloc.h>
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15 #endif
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16
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17 #ifdef HAVE_STRING_H
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18 #include <string.h>
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19 #endif
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20
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21 #ifdef USE_THREADS
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22
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23 #include <pthread.h>
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24
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25 #define ITEMS_PER_ALLOC 64
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26
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27 /* An item in the connection queue. */
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28 typedef struct conn_queue_item CQ_ITEM;
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29 struct conn_queue_item {
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30 int sfd;
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31 int init_state;
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32 int event_flags;
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33 int read_buffer_size;
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34 int is_udp;
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35 CQ_ITEM *next;
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36 };
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37
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38 /* A connection queue. */
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39 typedef struct conn_queue CQ;
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40 struct conn_queue {
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41 CQ_ITEM *head;
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42 CQ_ITEM *tail;
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43 pthread_mutex_t lock;
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44 pthread_cond_t cond;
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45 };
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46
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47 /* Lock for connection freelist */
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48 static pthread_mutex_t conn_lock;
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49
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50 /* Lock for cache operations (item_*, assoc_*) */
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51 static pthread_mutex_t cache_lock;
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52
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53 /* Lock for slab allocator operations */
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54 static pthread_mutex_t slabs_lock;
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55
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56 /* Lock for global stats */
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57 static pthread_mutex_t stats_lock;
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58
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59 /* Free list of CQ_ITEM structs */
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60 static CQ_ITEM *cqi_freelist;
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61 static pthread_mutex_t cqi_freelist_lock;
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62
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63 /*
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64 * Each libevent instance has a wakeup pipe, which other threads
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65 * can use to signal that they've put a new connection on its queue.
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66 */
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67 typedef struct {
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68 pthread_t thread_id; /* unique ID of this thread */
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69 struct event_base *base; /* libevent handle this thread uses */
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70 struct event notify_event; /* listen event for notify pipe */
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71 int notify_receive_fd; /* receiving end of notify pipe */
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72 int notify_send_fd; /* sending end of notify pipe */
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73 CQ new_conn_queue; /* queue of new connections to handle */
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74 } LIBEVENT_THREAD;
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75
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76 static LIBEVENT_THREAD *threads;
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77
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78 /*
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79 * Number of threads that have finished setting themselves up.
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80 */
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81 static int init_count = 0;
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82 static pthread_mutex_t init_lock;
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83 static pthread_cond_t init_cond;
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84
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85
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86 static void thread_libevent_process(int fd, short which, void *arg);
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87
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88 /*
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89 * Initializes a connection queue.
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90 */
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91 static void cq_init(CQ *cq) {
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92 pthread_mutex_init(&cq->lock, NULL);
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93 pthread_cond_init(&cq->cond, NULL);
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94 cq->head = NULL;
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95 cq->tail = NULL;
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96 }
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97
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98 /*
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99 * Waits for work on a connection queue.
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100 */
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101 static CQ_ITEM *cq_pop(CQ *cq) {
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102 CQ_ITEM *item;
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103
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104 pthread_mutex_lock(&cq->lock);
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105 while (NULL == cq->head)
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106 pthread_cond_wait(&cq->cond, &cq->lock);
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107 item = cq->head;
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108 cq->head = item->next;
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109 if (NULL == cq->head)
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110 cq->tail = NULL;
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111 pthread_mutex_unlock(&cq->lock);
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112
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113 return item;
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114 }
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115
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116 /*
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117 * Looks for an item on a connection queue, but doesn't block if there isn't
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118 * one.
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119 * Returns the item, or NULL if no item is available
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120 */
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121 static CQ_ITEM *cq_peek(CQ *cq) {
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122 CQ_ITEM *item;
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123
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124 pthread_mutex_lock(&cq->lock);
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125 item = cq->head;
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126 if (NULL != item) {
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127 cq->head = item->next;
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128 if (NULL == cq->head)
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129 cq->tail = NULL;
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130 }
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131 pthread_mutex_unlock(&cq->lock);
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132
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133 return item;
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134 }
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135
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136 /*
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137 * Adds an item to a connection queue.
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138 */
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139 static void cq_push(CQ *cq, CQ_ITEM *item) {
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140 item->next = NULL;
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141
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142 pthread_mutex_lock(&cq->lock);
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143 if (NULL == cq->tail)
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144 cq->head = item;
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145 else
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146 cq->tail->next = item;
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147 cq->tail = item;
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148 pthread_cond_signal(&cq->cond);
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149 pthread_mutex_unlock(&cq->lock);
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150 }
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151
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152 /*
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153 * Returns a fresh connection queue item.
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154 */
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155 static CQ_ITEM *cqi_new() {
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156 CQ_ITEM *item = NULL;
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157 pthread_mutex_lock(&cqi_freelist_lock);
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158 if (cqi_freelist) {
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159 item = cqi_freelist;
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160 cqi_freelist = item->next;
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161 }
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162 pthread_mutex_unlock(&cqi_freelist_lock);
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163
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164 if (NULL == item) {
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165 int i;
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166
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167 /* Allocate a bunch of items at once to reduce fragmentation */
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168 item = malloc(sizeof(CQ_ITEM) * ITEMS_PER_ALLOC);
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169 if (NULL == item)
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170 return NULL;
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171
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172 /*
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173 * Link together all the new items except the first one
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174 * (which we'll return to the caller) for placement on
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175 * the freelist.
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176 */
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177 for (i = 2; i < ITEMS_PER_ALLOC; i++)
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178 item[i - 1].next = &item[i];
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179
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180 pthread_mutex_lock(&cqi_freelist_lock);
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181 item[ITEMS_PER_ALLOC - 1].next = cqi_freelist;
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182 cqi_freelist = &item[1];
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183 pthread_mutex_unlock(&cqi_freelist_lock);
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184 }
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185
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186 return item;
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187 }
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188
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189
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190 /*
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191 * Frees a connection queue item (adds it to the freelist.)
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192 */
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193 static void cqi_free(CQ_ITEM *item) {
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194 pthread_mutex_lock(&cqi_freelist_lock);
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195 item->next = cqi_freelist;
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196 cqi_freelist = item;
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197 pthread_mutex_unlock(&cqi_freelist_lock);
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198 }
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199
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200
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201 /*
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202 * Creates a worker thread.
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203 */
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204 static void create_worker(void *(*func)(void *), void *arg) {
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205 pthread_t thread;
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206 pthread_attr_t attr;
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207 int ret;
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208
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209 pthread_attr_init(&attr);
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210
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211 if ((ret = pthread_create(&thread, &attr, func, arg)) != 0) {
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212 fprintf(stderr, "Can't create thread: %s\n",
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213 strerror(ret));
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214 exit(1);
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215 }
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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 * Pulls a conn structure from the freelist, if one is available.
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221 */
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222 conn *mt_conn_from_freelist() {
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223 conn *c;
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224
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225 pthread_mutex_lock(&conn_lock);
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226 c = do_conn_from_freelist();
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227 pthread_mutex_unlock(&conn_lock);
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228
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229 return c;
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230 }
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231
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232
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233 /*
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234 * Adds a conn structure to the freelist.
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235 *
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236 * Returns 0 on success, 1 if the structure couldn't be added.
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237 */
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238 int mt_conn_add_to_freelist(conn *c) {
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239 int result;
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240
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241 pthread_mutex_lock(&conn_lock);
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242 result = do_conn_add_to_freelist(c);
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243 pthread_mutex_unlock(&conn_lock);
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244
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245 return result;
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246 }
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247
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248 /****************************** LIBEVENT THREADS *****************************/
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249
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250 /*
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251 * Set up a thread's information.
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252 */
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253 static void setup_thread(LIBEVENT_THREAD *me) {
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254 if (! me->base) {
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255 me->base = event_init();
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256 if (! me->base) {
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257 fprintf(stderr, "Can't allocate event base\n");
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258 exit(1);
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259 }
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260 }
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261
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262 /* Listen for notifications from other threads */
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263 event_set(&me->notify_event, me->notify_receive_fd,
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264 EV_READ | EV_PERSIST, thread_libevent_process, me);
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265 event_base_set(me->base, &me->notify_event);
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266
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267 if (event_add(&me->notify_event, 0) == -1) {
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268 fprintf(stderr, "Can't monitor libevent notify pipe\n");
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269 exit(1);
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270 }
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271
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272 cq_init(&me->new_conn_queue);
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273 }
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274
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275
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276 /*
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277 * Worker thread: main event loop
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278 */
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279 static void *worker_libevent(void *arg) {
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280 LIBEVENT_THREAD *me = arg;
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281
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282 /* Any per-thread setup can happen here; thread_init() will block until
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283 * all threads have finished initializing.
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284 */
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285
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286 pthread_mutex_lock(&init_lock);
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287 init_count++;
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288 pthread_cond_signal(&init_cond);
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289 pthread_mutex_unlock(&init_lock);
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290
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291 return (void*) event_base_loop(me->base, 0);
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292 }
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293
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294
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295 /*
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296 * Processes an incoming "handle a new connection" item. This is called when
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297 * input arrives on the libevent wakeup pipe.
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298 */
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299 static void thread_libevent_process(int fd, short which, void *arg) {
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300 LIBEVENT_THREAD *me = arg;
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301 CQ_ITEM *item;
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302 char buf[1];
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303
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304 if (read(fd, buf, 1) != 1)
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305 if (settings.verbose > 0)
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306 fprintf(stderr, "Can't read from libevent pipe\n");
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307
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308 item = cq_peek(&me->new_conn_queue);
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309
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310 if (NULL != item) {
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311 conn *c = conn_new(item->sfd, item->init_state, item->event_flags,
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312 item->read_buffer_size, item->is_udp, me->base);
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313 if (!c) {
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314 if (item->is_udp) {
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315 fprintf(stderr, "Can't listen for events on UDP socket\n");
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316 exit(1);
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317 } else {
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318 if (settings.verbose > 0) {
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319 fprintf(stderr, "Can't listen for events on fd %d\n",
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320 item->sfd);
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321 }
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322 close(item->sfd);
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323 }
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324 }
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325 cqi_free(item);
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326 }
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327 }
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328
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329 /* Which thread we assigned a connection to most recently. */
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330 static int last_thread = -1;
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331
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332 /*
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333 * Dispatches a new connection to another thread. This is only ever called
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334 * from the main thread, either during initialization (for UDP) or because
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335 * of an incoming connection.
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336 */
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337 void dispatch_conn_new(int sfd, int init_state, int event_flags,
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338 int read_buffer_size, int is_udp) {
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339 CQ_ITEM *item = cqi_new();
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340 int thread = (last_thread + 1) % settings.num_threads;
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341
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342 last_thread = thread;
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343
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344 item->sfd = sfd;
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345 item->init_state = init_state;
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346 item->event_flags = event_flags;
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347 item->read_buffer_size = read_buffer_size;
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348 item->is_udp = is_udp;
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349
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350 cq_push(&threads[thread].new_conn_queue, item);
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351 if (write(threads[thread].notify_send_fd, "", 1) != 1) {
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352 perror("Writing to thread notify pipe");
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353 }
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354 }
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355
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356 /*
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357 * Returns true if this is the thread that listens for new TCP connections.
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358 */
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359 int mt_is_listen_thread() {
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360 return pthread_self() == threads[0].thread_id;
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361 }
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362
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363 /********************************* ITEM ACCESS *******************************/
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364
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365 /*
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366 * Walks through the list of deletes that have been deferred because the items
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367 * were locked down at the tmie.
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368 */
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369 void mt_run_deferred_deletes() {
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370 pthread_mutex_lock(&cache_lock);
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371 do_run_deferred_deletes();
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372 pthread_mutex_unlock(&cache_lock);
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373 }
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374
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375 /*
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376 * Allocates a new item.
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377 */
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378 item *mt_item_alloc(char *key, size_t nkey, int flags, rel_time_t exptime, int nbytes) {
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379 item *it;
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380 pthread_mutex_lock(&cache_lock);
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381 it = do_item_alloc(key, nkey, flags, exptime, nbytes);
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382 pthread_mutex_unlock(&cache_lock);
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383 return it;
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384 }
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385
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386 /*
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387 * Returns an item if it hasn't been marked as expired or deleted,
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388 * lazy-expiring as needed.
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389 */
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390 item *mt_item_get_notedeleted(const char *key, const size_t nkey, bool *delete_locked) {
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391 item *it;
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392 pthread_mutex_lock(&cache_lock);
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393 it = do_item_get_notedeleted(key, nkey, delete_locked);
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394 pthread_mutex_unlock(&cache_lock);
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395 return it;
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396 }
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397
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398 /*
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399 * Links an item into the LRU and hashtable.
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400 */
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401 int mt_item_link(item *item) {
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402 int ret;
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403
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404 pthread_mutex_lock(&cache_lock);
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405 ret = do_item_link(item);
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406 pthread_mutex_unlock(&cache_lock);
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407 return ret;
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408 }
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409
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410 /*
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411 * Decrements the reference count on an item and adds it to the freelist if
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412 * needed.
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413 */
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414 void mt_item_remove(item *item) {
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415 pthread_mutex_lock(&cache_lock);
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416 do_item_remove(item);
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417 pthread_mutex_unlock(&cache_lock);
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418 }
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419
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420 /*
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421 * Replaces one item with another in the hashtable.
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422 */
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423 int mt_item_replace(item *old, item *new) {
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424 int ret;
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425
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426 pthread_mutex_lock(&cache_lock);
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427 ret = do_item_replace(old, new);
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428 pthread_mutex_unlock(&cache_lock);
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429 return ret;
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430 }
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431
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432 /*
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433 * Unlinks an item from the LRU and hashtable.
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434 */
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435 void mt_item_unlink(item *item) {
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436 pthread_mutex_lock(&cache_lock);
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437 do_item_unlink(item);
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438 pthread_mutex_unlock(&cache_lock);
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439 }
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440
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441 /*
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442 * Moves an item to the back of the LRU queue.
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443 */
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444 void mt_item_update(item *item) {
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445 pthread_mutex_lock(&cache_lock);
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446 do_item_update(item);
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447 pthread_mutex_unlock(&cache_lock);
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448 }
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449
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450 /*
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451 * Adds an item to the deferred-delete list so it can be reaped later.
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452 */
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453 char *mt_defer_delete(item *item, time_t exptime) {
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454 char *ret;
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455
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456 pthread_mutex_lock(&cache_lock);
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457 ret = do_defer_delete(item, exptime);
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458 pthread_mutex_unlock(&cache_lock);
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459 return ret;
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460 }
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461
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462 /*
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463 * Does arithmetic on a numeric item value.
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464 */
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465 char *mt_add_delta(item *item, int incr, unsigned int delta, char *buf) {
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466 char *ret;
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467
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468 pthread_mutex_lock(&cache_lock);
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469 ret = do_add_delta(item, incr, delta, buf);
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470 pthread_mutex_unlock(&cache_lock);
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471 return ret;
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472 }
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473
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474 /*
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475 * Stores an item in the cache (high level, obeys set/add/replace semantics)
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476 */
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477 int mt_store_item(item *item, int comm) {
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478 int ret;
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479
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480 pthread_mutex_lock(&cache_lock);
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481 ret = do_store_item(item, comm);
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482 pthread_mutex_unlock(&cache_lock);
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483 return ret;
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484 }
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485
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486 /*
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487 * Flushes expired items after a flush_all call
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488 */
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489 void mt_item_flush_expired() {
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490 pthread_mutex_lock(&cache_lock);
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491 do_item_flush_expired();
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492 pthread_mutex_unlock(&cache_lock);
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493 }
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494
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495 /****************************** HASHTABLE MODULE *****************************/
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496
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497 void mt_assoc_move_next_bucket() {
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498 pthread_mutex_lock(&cache_lock);
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499 do_assoc_move_next_bucket();
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500 pthread_mutex_unlock(&cache_lock);
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501 }
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502
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503 /******************************* SLAB ALLOCATOR ******************************/
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504
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505 void *mt_slabs_alloc(size_t size) {
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506 void *ret;
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507
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508 pthread_mutex_lock(&slabs_lock);
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509 ret = do_slabs_alloc(size);
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510 pthread_mutex_unlock(&slabs_lock);
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511 return ret;
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512 }
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513
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514 void mt_slabs_free(void *ptr, size_t size) {
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515 pthread_mutex_lock(&slabs_lock);
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516 do_slabs_free(ptr, size);
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517 pthread_mutex_unlock(&slabs_lock);
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518 }
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519
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520 char *mt_slabs_stats(int *buflen) {
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521 char *ret;
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522
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523 pthread_mutex_lock(&slabs_lock);
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524 ret = do_slabs_stats(buflen);
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525 pthread_mutex_unlock(&slabs_lock);
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|
526 return ret;
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527 }
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528
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|
529 #ifdef ALLOW_SLABS_REASSIGN
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|
530 int mt_slabs_reassign(unsigned char srcid, unsigned char dstid) {
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|
531 int ret;
|
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532
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533 pthread_mutex_lock(&slabs_lock);
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534 ret = do_slabs_reassign(srcid, dstid);
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535 pthread_mutex_unlock(&slabs_lock);
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|
536 return ret;
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537 }
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538 #endif
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539
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540 /******************************* GLOBAL STATS ******************************/
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541
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542 void mt_stats_lock() {
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543 pthread_mutex_lock(&stats_lock);
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|
544 }
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545
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546 void mt_stats_unlock() {
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547 pthread_mutex_unlock(&stats_lock);
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548 }
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|
549
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550 /*
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551 * Initializes the thread subsystem, creating various worker threads.
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|
552 *
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|
553 * nthreads Number of event handler threads to spawn
|
|
554 * main_base Event base for main thread
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|
555 */
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|
556 void thread_init(int nthreads, struct event_base *main_base) {
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|
557 int i;
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|
558
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|
559 pthread_mutex_init(&cache_lock, NULL);
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|
560 pthread_mutex_init(&conn_lock, NULL);
|
|
561 pthread_mutex_init(&slabs_lock, NULL);
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|
562 pthread_mutex_init(&stats_lock, NULL);
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|
563
|
|
564 pthread_mutex_init(&init_lock, NULL);
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|
565 pthread_cond_init(&init_cond, NULL);
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|
566
|
|
567 pthread_mutex_init(&cqi_freelist_lock, NULL);
|
|
568 cqi_freelist = NULL;
|
|
569
|
|
570 threads = malloc(sizeof(LIBEVENT_THREAD) * nthreads);
|
|
571 if (! threads) {
|
|
572 perror("Can't allocate thread descriptors");
|
|
573 exit(1);
|
|
574 }
|
|
575
|
|
576 threads[0].base = main_base;
|
|
577 threads[0].thread_id = pthread_self();
|
|
578
|
|
579 for (i = 0; i < nthreads; i++) {
|
|
580 int fds[2];
|
|
581 if (pipe(fds)) {
|
|
582 perror("Can't create notify pipe");
|
|
583 exit(1);
|
|
584 }
|
|
585
|
|
586 threads[i].notify_receive_fd = fds[0];
|
|
587 threads[i].notify_send_fd = fds[1];
|
|
588
|
|
589 setup_thread(&threads[i]);
|
|
590 }
|
|
591
|
|
592 /* Create threads after we've done all the libevent setup. */
|
|
593 for (i = 1; i < nthreads; i++) {
|
|
594 create_worker(worker_libevent, &threads[i]);
|
|
595 }
|
|
596
|
|
597 /* Wait for all the threads to set themselves up before returning. */
|
|
598 pthread_mutex_lock(&init_lock);
|
|
599 init_count++; // main thread
|
|
600 while (init_count < nthreads) {
|
|
601 pthread_cond_wait(&init_cond, &init_lock);
|
|
602 }
|
|
603 pthread_mutex_unlock(&init_lock);
|
|
604 }
|
|
605
|
|
606 #endif
|