1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71

int freeMemoryIfNeeded(void){while (mem_freed < mem_tofree) {if (server.maxmemory_policy == REDIS_MAXMEMORY_NO_EVICTION)return REDIS_ERR; /* We need to free memory, but policy forbids. */if (server.maxmemory_policy == REDIS_MAXMEMORY_ALLKEYS_LRU ||server.maxmemory_policy == REDIS_MAXMEMORY_ALLKEYS_RANDOM){......}/* volatile-random and allkeys-random policy */if (server.maxmemory_policy == REDIS_MAXMEMORY_ALLKEYS_RANDOM ||server.maxmemory_policy == REDIS_MAXMEMORY_VOLATILE_RANDOM){......}/* volatile-lru and allkeys-lru policy */else if (server.maxmemory_policy == REDIS_MAXMEMORY_ALLKEYS_LRU ||server.maxmemory_policy == REDIS_MAXMEMORY_VOLATILE_LRU){// 淘汰池函数evictionPoolPopulate(dict, db->dict, db->eviction_pool);while(bestkey == NULL) {evictionPoolPopulate(dict, db->dict, db->eviction_pool);// 从后向前逐一淘汰for (k = REDIS_EVICTION_POOL_SIZE-1; k >= 0; k--) {if (pool[k].key == NULL) continue;de = dictFind(dict,pool[k].key); // 定位目标/* Remove the entry from the pool. */sdsfree(pool[k].key);/* Shift all elements on its right to left. */memmove(pool+k,pool+k+1,sizeof(pool[0])*(REDIS_EVICTION_POOL_SIZE-k-1));/* Clear the element on the right which is empty* since we shifted one position to the left.  */pool[REDIS_EVICTION_POOL_SIZE-1].key = NULL;pool[REDIS_EVICTION_POOL_SIZE-1].idle = 0;/* If the key exists, is our pick. Otherwise it is* a ghost and we need to try the next element. */if (de) {bestkey = dictGetKey(de); // 确定删除键break;} else {/* Ghost... */continue;}}}}/* volatile-ttl */else if (server.maxmemory_policy == EDIS_MAXMEMORY_VOLATILE_TTL) {......}// 最终选定待删除键bestkeyif (bestkey) {long long delta;robj *keyobj = createStringObject(bestkey,sdslenbestkey)); // 目标对象propagateExpire(db,keyobj);latencyStartMonitor(eviction_latency); // 延迟监控开始dbDelete(db,keyobj); // 从db删除对象latencyEndMonitor(eviction_latency);// 延迟监控结束latencyAddSampleIfNeeded("eviction-del",iction_latency); // 延迟采样latencyRemoveNestedEvent(latency,eviction_latency);delta -= (long long) zmalloc_used_memory();mem_freed += delta; // 释放内存计数server.stat_evictedkeys++; // 淘汰key计数，info中可见notifyKeyspaceEvent(REDIS_NOTIFY_EVICTED, "evicted", keyobj, db->id); // 事件通知decrRefCount(keyobj); // 引用计数更新keys_freed++;// 避免删除较多键导致的主从延迟，在循环内同步if (slaves) flushSlavesOutputBuffers();}}
}