Function performEvictions

src/evict.cpp:667–965

Check that memory usage is within the current "maxmemory" limit. If over * "maxmemory", attempt to free memory by evicting data (if it's safe to do so). * * It's possible for Redis to suddenly be significantly over the "maxmemory" * setting. This can happen if there is a large allocation (like a hash table * resize) or even if the "maxmemory" setting is manually adjusted. Because of * thi

 *   EVICT_FAIL     - memory is over the limit, and there's nothing to evict
 * */
int performEvictions(bool fPreSnapshot) {
    if (!isSafeToPerformEvictions()) return EVICT_OK;
    serverAssert(GlobalLocksAcquired());

    int keys_freed = 0;
    size_t mem_reported, mem_tofree;
    long long mem_freed; /* May be negative */
    mstime_t latency;
    long long delta;
    int slaves = listLength(g_pserver->slaves);
    const bool fEvictToStorage = !cserver.delete_on_evict && g_pserver->db[0]->FStorageProvider();
    int result = EVICT_FAIL;
    int ckeysFailed = 0;
    EvictReason evictReason;

    std::unique_ptr<FreeMemoryLazyFree> splazy = std::make_unique<FreeMemoryLazyFree>();

    if (getMaxmemoryState(&mem_reported,NULL,&mem_tofree,NULL,&evictReason,false,fPreSnapshot) == C_OK)
        return EVICT_OK;

    if (g_pserver->maxmemory_policy == MAXMEMORY_NO_EVICTION)
        return EVICT_FAIL;  /* We need to free memory, but policy forbids. */

    unsigned long eviction_time_limit_us = evictionTimeLimitUs();

    mem_freed = 0;

    latencyStartMonitor(latency);

    monotime evictionTimer;
    elapsedStart(&evictionTimer);

    if (g_pserver->maxstorage && g_pserver->m_pstorageFactory != nullptr) {
        while (g_pserver->m_pstorageFactory->totalDiskspaceUsed() >= g_pserver->maxstorage && elapsedUs(evictionTimer) < eviction_time_limit_us) {
            redisDb *db;
            std::vector<std::string> evictionPool;
            robj *bestkey = nullptr;
            redisDb *bestdb = nullptr;
            unsigned long long bestidle = 0;
            for (int i = 0; i < cserver.dbnum; i++) {
                db = g_pserver->db[i];
                evictionPool = db->getStorageCache()->getEvictionCandidates(g_pserver->maxmemory_samples);
                for (std::string key : evictionPool) {
                    robj *keyobj = createStringObject(key.c_str(), key.size());
                    robj *obj = db->find(szFromObj(keyobj));
                    if (obj != nullptr) {
                        expireEntry *e = db->getExpire(keyobj);
                        unsigned long long idle = getIdle(obj, e);

                        if (bestkey == nullptr || bestidle < idle) {
                            if (bestkey != nullptr)
                                decrRefCount(bestkey);
                            incrRefCount(keyobj);
                            bestkey = keyobj;
                            bestidle = idle;
                            bestdb = db;
                        }
                    }