Thread.sleep takes lot of CPU time!

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Raga - 17 Jul 2006 14:49 GMT

Hi,

I have the run method like this:

....
....
public void run()
{
...

while(true)
{
...
//some set of operations
....

Thread.sleep(5*1000*60);

}

In the above code, the sleep operation seems to take a lot of CPU time
though ideally sleep is like a no-op mode, meaning since no operation
is done when a thread sleeps, it should not use any/minimal CPU time.
But it seems to take over 30% of CPU time!

Any ideas on why such a weird thing's happening?

In fact, in one more similar method also, sleep is taking similar CPU
time.

Reply to this Message

Philipp Leitner - 17 Jul 2006 15:05 GMT

> Hi,
>
[quoted text clipped - 25 lines]
> In fact, in one more similar method also, sleep is taking similar CPU
> time.

Hmmm ... no, on my computer (Mac OS X 10.4, Java 5) I don't have
similar problems:

I wrote something like

public class ThreadTest {
public static void main(String[] args) {
try {
for(;;)
Thread.sleep(5*1000*60);
}
catch(Exception e) {
e.printStackTrace();
}
}
}

to test it, and it does not seem to consume much CPU while sleeping:

902 java 0.0% 0:00.50

/philipp

Reply to this Message

Raga - 18 Jul 2006 07:10 GMT

Hi Philipp,

I checked the performance statistics when doing a stress test. Maybe,
doing a stress test yields such result??

Regards,
Raga

> > Hi,
> >
[quoted text clipped - 48 lines]
>
> /philipp

Reply to this Message

pranshu - 17 Jul 2006 17:02 GMT

Hi Raga,
How are you measuring CPU time ?

I guess you are using a profiler.
It is highly likely that your loop is very light - taking 0.01% of
system time - and out of that the sleep method is taking 30%?
essentially being 30% of nothing.

Pranshu

Reply to this Message

Raga - 18 Jul 2006 07:09 GMT

Yes, I used profiler.

Its not that way. Out of teh total CPU consumption, sleep() in this
method is taking about 30%, which is very high right? This was observed
when a stress test was done. Has it something to do specifically when
stress testing?

Regards,
Raga

> Hi Raga,
> How are you measuring CPU time ?
[quoted text clipped - 5 lines]
>
> Pranshu

Reply to this Message

Thread.sleep takes lot of CPU time!

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