Function objectSetLRUOrLFU

app/redis-6.2.6/src/object.c:1211–1237

Set the object LRU/LFU depending on server.maxmemory_policy. * The lfu_freq arg is only relevant if policy is MAXMEMORY_FLAG_LFU. * The lru_idle and lru_clock args are only relevant if policy * is MAXMEMORY_FLAG_LRU. * Either or both of them may be <0, in that case, nothing is set. */

 * is MAXMEMORY_FLAG_LRU.
 * Either or both of them may be <0, in that case, nothing is set. */
int objectSetLRUOrLFU(robj *val, long long lfu_freq, long long lru_idle,
                       long long lru_clock, int lru_multiplier) {
    if (server.maxmemory_policy & MAXMEMORY_FLAG_LFU) {
        if (lfu_freq >= 0) {
            serverAssert(lfu_freq <= 255);
            val->lru = (LFUGetTimeInMinutes()<<8) | lfu_freq;
            return 1;
        }
    } else if (lru_idle >= 0) {
        /* Provided LRU idle time is in seconds. Scale
         * according to the LRU clock resolution this Redis
         * instance was compiled with (normally 1000 ms, so the
         * below statement will expand to lru_idle*1000/1000. */
        lru_idle = lru_idle*lru_multiplier/LRU_CLOCK_RESOLUTION;
        long lru_abs = lru_clock - lru_idle; /* Absolute access time. */
        /* If the LRU field underflows (since LRU it is a wrapping
         * clock), the best we can do is to provide a large enough LRU
         * that is half-way in the circlular LRU clock we use: this way
         * the computed idle time for this object will stay high for quite
         * some time. */
        if (lru_abs < 0)
            lru_abs = (lru_clock+(LRU_CLOCK_MAX/2)) % LRU_CLOCK_MAX;
        val->lru = lru_abs;
        return 1;
    }
    return 0;
}

/* ======================= The OBJECT and MEMORY commands =================== */