**Motivation:**
When examining the serialized design of NioEventLoop, during the
execution of the runAllTasks method within the run method, expired tasks
are first transferred to the taskQueue. After that, tasks are retrieved
from the taskQueue and executed.

During the task transfer process, if it is discovered that the current
taskQueue is full, the retrieved tasks are put back into the delayed
tasks queue. However, upon retrieval, there is a setConsumed method
called. In this particular scenario, the task is actually not consumed,
which begs the question: Could this have any implications?

 After clicking to view the comments：
“Optimization to avoid checking system clock again，after deadline has
passed and task has been dequeued“

Based on the comments, it is speculated that when a task is executed or
re-enqueued, it might involve checking the system clock. After
conducting a thorough investigation, it was found that this could be
related to the task's own run method.
io.netty.util.concurrent.ScheduledFutureTask#run
io.netty.util.concurrent.ScheduledFutureTask#delayNanos()

 `public void run() {
         ...
            if (delayNanos() > 0L) 
        ...
}`

`public long delayNanos() {
        return delayNanos(scheduledExecutor().getCurrentTimeNanos());
    }`

`static long deadlineToDelayNanos(long currentTimeNanos, long
deadlineNanos) {
return deadlineNanos == 0L ? 0L : Math.max(0L, deadlineNanos -
currentTimeNanos);
    }`

   ` public long delayNanos(long currentTimeNanos) {
        return deadlineToDelayNanos(currentTimeNanos, deadlineNanos);
    }`
    
If this is indeed the case, then the optimization brought about is
merely reducing a single computation and does not involve the system
clock.

**Modification:**
Therefore, I suggest adding a pre-check here. If the current delayNanos
equals 0L, we can directly return without proceeding, thus reducing the
computation involving the system clock.
` public long delayNanos() {
        if(deadlineNanos == 0L){
            return 0L;
        }
        return delayNanos(scheduledExecutor().getCurrentTimeNanos());
    }`

**Result:**
Reducing the number of invocations by the amount of expired tasks that
are now bypassed, would lead to an overall significant benefit.
Describe the modifications you've done.

---------

Co-authored-by: Norman Maurer <norman_maurer@apple.com>