protected void run() {
    for (;;) {
        try {
            switch (selectStrategy.calculateStrategy(selectNowSupplier, hasTasks())) {
                case SelectStrategy.CONTINUE:
                    continue;
                case SelectStrategy.SELECT:
                    //輪詢io事件(1)
                    select(wakenUp.getAndSet(false));
                    if (wakenUp.get()) {
                        selector.wakeup();
                    }
                default:
            }
            cancelledKeys = 0;
            needsToSelectAgain = false;
            //默認是50
            final int ioRatio = this.ioRatio; 
            if (ioRatio == 100) {
                try {
                    processSelectedKeys();
                } finally {
                    runAllTasks();
                }
            } else {
                //記錄下開始時間
                final long ioStartTime = System.nanoTime();
                try {
                    //處理輪詢到的key(2)
                    processSelectedKeys();
                } finally {
                    //計算耗時
                    final long ioTime = System.nanoTime() - ioStartTime;
                    //執(zhí)行task(3)
                    runAllTasks(ioTime * (100 - ioRatio) / ioRatio);
                }
            }
        } catch (Throwable t) {
            handleLoopException(t);
        }
        //代碼省略
    }
}

private void select(boolean oldWakenUp) throws IOException {
    Selector selector = this.selector;
    try {
        int selectCnt = 0;
        //當(dāng)前系統(tǒng)的納秒數(shù)
        long currentTimeNanos = System.nanoTime();
        //截止時間=當(dāng)前時間+隊列第一個任務(wù)剩余執(zhí)行時間
        long selectDeadLineNanos = currentTimeNanos + delayNanos(currentTimeNanos);
        for (;;) {
            //阻塞時間(毫秒)=(截止時間-當(dāng)前時間+0.5毫秒)
            long timeoutMillis = (selectDeadLineNanos - currentTimeNanos + 500000L) / 1000000L;
            if (timeoutMillis <= 0) {
                if (selectCnt == 0) {
                    selector.selectNow();
                    selectCnt = 1;
                }
                break;
            }
            if (hasTasks() && wakenUp.compareAndSet(false, true)) {
                selector.selectNow();
                selectCnt = 1;
                break;
            }
            //進行阻塞式的select操作
            int selectedKeys = selector.select(timeoutMillis);
            //輪詢次數(shù)
            selectCnt ++;
            //如果輪詢到一個事件(selectedKeys != 0), 或者當(dāng)前select操作需要喚醒(oldWakenUp), 
            //或者在執(zhí)行select操作時已經(jīng)被外部線程喚醒(wakenUp.get()), 
            //或者任務(wù)隊列已經(jīng)有任務(wù)(hasTask), 或者定時任務(wù)隊列中有任務(wù)(hasScheduledTasks())
            if (selectedKeys != 0 || oldWakenUp || wakenUp.get() || hasTasks() || hasScheduledTasks()) {
                break;
            }
            //省略
            //記錄下當(dāng)前時間
            long time = System.nanoTime();
            //當(dāng)前時間-開始時間>=超時時間(條件成立, 執(zhí)行過一次select操作, 條件不成立, 有可能發(fā)生空輪詢)
            if (time - TimeUnit.MILLISECONDS.toNanos(timeoutMillis) >= currentTimeNanos) {
                //代表已經(jīng)進行了一次阻塞式select操作, 操作次數(shù)重置為1
                selectCnt = 1;
            } else if (SELECTOR_AUTO_REBUILD_THRESHOLD > 0 && selectCnt >= SELECTOR_AUTO_REBUILD_THRESHOLD) {
                //省略日志代碼
                //如果空輪詢的次數(shù)大于一個閾值(512), 解決空輪詢的bug
                rebuildSelector();
                selector = this.selector;
                selector.selectNow();
                selectCnt = 1;
                break;
            }
            currentTimeNanos = time;
        }
        //代碼省略
    } catch (CancelledKeyException e) {
        //省略
    }
}

public void rebuildSelector() {
    //是否是由其他線程發(fā)起的
    if (!inEventLoop()) {
        //如果是其他線程發(fā)起的, 將rebuildSelector()封裝成任務(wù)隊列, 由NioEventLoop進行調(diào)用
        execute(new Runnable() {
            @Override
            public void run() {
                rebuildSelector();
            }
        });
        return;
    }
    final Selector oldSelector = selector;
    final Selector newSelector;
    if (oldSelector == null) {
        return;
    }
    try {
        //重新創(chuàng)建一個select
        newSelector = openSelector();
    } catch (Exception e) {
        logger.warn("Failed to create a new Selector.", e);
        return;
    }
    int nChannels = 0;
    for (;;) {
        try {
            //拿到舊select中所有的key
            for (SelectionKey key: oldSelector.keys()) {
                Object a = key.attachment();
                try {
                    Object a = key.attachment();
                    //代碼省略

                    //獲取key注冊的事件
                    int interestOps = key.interestOps();
                    //將key注冊的事件取消
                    key.cancel();
                    //注冊到重新創(chuàng)建的新的selector中
                    SelectionKey newKey = key.channel().register(newSelector, interestOps, a);
                    //如果channel是NioChannel
                    if (a instanceof AbstractNioChannel) {
                        //重新賦值
                        ((AbstractNioChannel) a).selectionKey = newKey;
                    }
                    nChannels ++;
                } catch (Exception e) {
                    //代碼省略
                }
            }
        } catch (ConcurrentModificationException e) {
            continue;
        }
        break;
    }
    selector = newSelector;
    //代碼省略
}