Function computeDefragCycles

app/redis-6.2.6/src/defrag.c:1046–1074

decide if defrag is needed, and at what CPU effort to invest in it */

/* decide if defrag is needed, and at what CPU effort to invest in it */
void computeDefragCycles() {
    size_t frag_bytes;
    float frag_pct = getAllocatorFragmentation(&frag_bytes);
    /* If we're not already running, and below the threshold, exit. */
    if (!server.active_defrag_running) {
        if(frag_pct < server.active_defrag_threshold_lower || frag_bytes < server.active_defrag_ignore_bytes)
            return;
    }

    /* Calculate the adaptive aggressiveness of the defrag */
    int cpu_pct = INTERPOLATE(frag_pct,
            server.active_defrag_threshold_lower,
            server.active_defrag_threshold_upper,
            server.active_defrag_cycle_min,
            server.active_defrag_cycle_max);
    cpu_pct = LIMIT(cpu_pct,
            server.active_defrag_cycle_min,
            server.active_defrag_cycle_max);
     /* We allow increasing the aggressiveness during a scan, but don't
      * reduce it. */
    if (!server.active_defrag_running ||
        cpu_pct > server.active_defrag_running)
    {
        server.active_defrag_running = cpu_pct;
        serverLog(LL_VERBOSE,
            "Starting active defrag, frag=%.0f%%, frag_bytes=%zu, cpu=%d%%",
            frag_pct, frag_bytes, cpu_pct);
    }
}

/* Perform incremental defragmentation work from the serverCron.
 * This works in a similar way to activeExpireCycle, in the sense that