int handleClientsWithPendingReadsUsingThreads(void) {
    if (!server.io_threads_active || !server.io_threads_do_reads) return 0;
    int processed = listLength(server.clients_pending_read);
    if (processed == 0) return 0;

    if (tio_debug) printf("%d TOTAL READ pending clients\n", processed);

    /* Distribute the clients across N different lists. */
    listIter li;
    listNode *ln;
    listRewind(server.clients_pending_read,&li);
    int item_id = 0;
    while((ln = listNext(&li))) {
        client *c = listNodeValue(ln);
        int target_id = item_id % server.io_threads_num;
        listAddNodeTail(io_threads_list[target_id],c);
        item_id++;
    }

    /* Give the start condition to the waiting threads, by setting the
     * start condition atomic var. */
    io_threads_op = IO_THREADS_OP_READ;
    for (int j = 1; j < server.io_threads_num; j++) {
        int count = listLength(io_threads_list[j]);
        io_threads_pending[j] = count;
    }

    /* Also use the main thread to process a slice of clients. */
    listRewind(io_threads_list[0],&li);
    while((ln = listNext(&li))) {
        client *c = listNodeValue(ln);
        readQueryFromClient(c->conn);
    }
    listEmpty(io_threads_list[0]);

    /* Wait for all the other threads to end their work. */
    while(1) {
        unsigned long pending = 0;
        for (int j = 1; j < server.io_threads_num; j++)
            pending += io_threads_pending[j];
        if (pending == 0) break;
    }
    if (tio_debug) printf("I/O READ All threads finshed\n");

    /* Run the list of clients again to process the new buffers. */
    while(listLength(server.clients_pending_read)) {
        ln = listFirst(server.clients_pending_read);
        client *c = listNodeValue(ln);
        c->flags &= ~CLIENT_PENDING_READ;
        listDelNode(server.clients_pending_read,ln);
        /* Clients can become paused while executing the queued commands,
         * so we need to check in between each command. If a pause was
         * executed, we still remove the command and it will get picked up
         * later when clients are unpaused and we re-queue all clients. */
        if (clientsArePaused()) continue;

        if (processPendingCommandsAndResetClient(c) == C_ERR) {
            /* If the client is no longer valid, we avoid
             * processing the client later. So we just go
             * to the next. */
            continue;
        }
        processInputBuffer(c);

        /* We may have pending replies if a thread readQueryFromClient() produced
         * replies and did not install a write handler (it can't).
         */
        if (!(c->flags & CLIENT_PENDING_WRITE) && clientHasPendingReplies(c))
            clientInstallWriteHandler(c);
    }

    /* Update processed count on server */
    server.stat_io_reads_processed += processed;

    return processed;
}
int handleClientsWithPendingReadsUsingThreads(void) {
    if (!server.io_threads_active || !server.io_threads_do_reads) return 0;
    int processed = listLength(server.clients_pending_read);
    if (processed == 0) return 0;

    if (tio_debug) printf("%d TOTAL READ pending clients\n", processed);

     
    listIter li;
    listNode *ln;
    listRewind(server.clients_pending_read,&li);
    int item_id = 0;
    while((ln = listNext(&li))) {
        client *c = listNodeValue(ln);
        int target_id = item_id % server.io_threads_num;
        listAddNodeTail(io_threads_list[target_id],c);
        item_id++;
    }

     
    io_threads_op = IO_THREADS_OP_READ;
    for (int j = 1; j < server.io_threads_num; j++) {
        int count = listLength(io_threads_list[j]);
        io_threads_pending[j] = count;
    }

     
    listRewind(io_threads_list[0],&li);
    while((ln = listNext(&li))) {
        client *c = listNodeValue(ln);
        readQueryFromClient(c->conn);
    }
    listEmpty(io_threads_list[0]);

     
    while(1) {
        unsigned long pending = 0;
        for (int j = 1; j < server.io_threads_num; j++)
            pending += io_threads_pending[j];
        if (pending == 0) break;
    }
    if (tio_debug) printf("I/O READ All threads finshed\n");

     
    while(listLength(server.clients_pending_read)) {
        ln = listFirst(server.clients_pending_read);
        client *c = listNodeValue(ln);
        c->flags &= ~CLIENT_PENDING_READ;
        listDelNode(server.clients_pending_read,ln);
         
        if (clientsArePaused()) continue;

        if (processPendingCommandsAndResetClient(c) == C_ERR) {
             
            continue;
        }
        processInputBuffer(c);

         
        if (!(c->flags & CLIENT_PENDING_WRITE) && clientHasPendingReplies(c))
            clientInstallWriteHandler(c);
    }

     
    server.stat_io_reads_processed += processed;

    return processed;
}