Redis 6.2和7渐进式逐出优化

MAXMEMORY_VOLATILE_LRU
MAXMEMORY_VOLATILE_LFU
MAXMEMORY_VOLATILE_TTL
MAXMEMORY_VOLATILE_RANDOM
MAXMEMORY_ALLKEYS_LRU
MAXMEMORY_ALLKEYS_LFU
MAXMEMORY_ALLKEYS_RANDOM
MAXMEMORY_NO_EVICTION
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使用内存 = used_memory - AOF缓冲区 - slave缓冲区
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./redis-cli debug populate 40 user 20971520
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        //开始计时
        elapsedStart(&evictionTimer);

        /* Finally remove the selected key. */
        if (bestkey) {
            db = server.db+bestdbid;
            robj *keyobj = createStringObject(bestkey,sdslen(bestkey));
            delta = (long long) zmalloc_used_memory();
            latencyStartMonitor(eviction_latency);
            if (server.lazyfree_lazy_eviction)
                dbAsyncDelete(db,keyobj);
            else
                dbSyncDelete(db,keyobj);
            delta -= (long long) zmalloc_used_memory();
            mem_freed += delta;
            keys_freed++;

            if (keys_freed % 16 == 0) {
                if (slaves) flushSlavesOutputBuffers();
                if (server.lazyfree_lazy_eviction) {
                    if (getMaxmemoryState(NULL,NULL,NULL,NULL) == C_OK) {
                        break;
                    }
                }

                /* After some time, exit the loop early - even if memory limit
                 * hasn't been reached.  If we suddenly need to free a lot of
                 * memory, don't want to spend too much time here.  */
                if (elapsedUs(evictionTimer) > eviction_time_limit_us) {
                    // We still need to free memory - start eviction timer proc
                    startEvictionTimeProc();
                    break;
                }
            }
        }
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static unsigned long evictionTimeLimitUs() {
    serverAssert(server.maxmemory_eviction_tenacity >= 0);
    serverAssert(server.maxmemory_eviction_tenacity <= 100);

    if (server.maxmemory_eviction_tenacity <= 10) {
        /* A linear progression from 0..500us */
        return 50uL * server.maxmemory_eviction_tenacity;
    }

    if (server.maxmemory_eviction_tenacity < 100) {
        /* A 15% geometric progression, resulting in a limit of ~2 min at tenacity==99  */
        return (unsigned long)(500.0 * pow(1.15, server.maxmemory_eviction_tenacity - 10.0));
    }

    return ULONG_MAX;   /* No limit to eviction time */
}
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static int isEvictionProcRunning = 0;
static int evictionTimeProc(struct aeEventLoop *eventLoop, long long id, void *clientData) {

    if (performEvictions() == EVICT_RUNNING) return 0;  /* keep evicting */

    /* For EVICT_OK - things are good, no need to keep evicting.
     * For EVICT_FAIL - there is nothing left to evict.  */
    isEvictionProcRunning = 0;
    return AE_NOMORE;
}

void startEvictionTimeProc(void) {
    if (!isEvictionProcRunning) {
        isEvictionProcRunning = 1;
        aeCreateTimeEvent(server.el, 0, evictionTimeProc, NULL, NULL);
    }
}
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* A new incremental eviction mechanism that reduces latency on eviction spikes (#7653)
  In pathological cases this can cause memory to grow uncontrolled and may require
  specific tuning.
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* Fix a hang when eviction is combined with lazy-free and maxmemory-eviction-tenacity
  is set to 100 (#11237)
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