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Unexpected 50ms delay for all jobs [message #1017225]

Mon, 11 March 2013 08:58

Leung Wang Hei

Messages: 64
Registered: July 2010

Member

Job is often found to be executed exactly 50ms after the scheduling time.

To reproduce:
1. Create a plugin project with RCP application with a view template
2. Replace of the attached View.java
3. Double click at any table item and schedule the job for 1 second.

Here is the output:

1362985303755 --- schedule job in ms: 1000
1362985303755 job scheduled
1362985304805 job about to run
1362985304805 --- do job.  Wait time=1050

Seems it is related to a 50 ms sleep in WorkerPool.startJob(Worker)

long hint = manager.sleepHint();  // return 0 if some jobs are waiting

...

job = manager.startJob();

...

//if we didn't sleep but there was no job available, make sure we sleep to avoid a tight loop (bug 260724)
if (hint <= 0 && job == null)
     sleep(50);

As said in bugzilla https://bugs.eclipse.org/bugs/show_bug.cgi?id=260724]:
Quote:

If the startJob() returns null, it implies the wait queue is empty and there are no sleeping jobs that are ready to run. The only case I can think of this happening is if multiple threads are awake at once in this loop. If there was one job waiting, the sleep hint would be 0 for all threads, but then only one thread will pop the job from the queue and the others will get null.

I break at the sleep(50) line and found the following sequence, not exactly as described above:

1. Schedule job for 1000ms
2. WorkPool triggered after 1000ms
3. sleepHint=0, job=null >> sleep(50)
4. Next iteration in the while loop
5. sleepHint= -ve, job=actual job object
6. Job done. 50ms after the expected schedule time.

Setting priority and user, system flag gives no difference.

Is there some setting in Job and/or JobManager causing this issue?