Issues running jcstress on multi-core systems

[Johnson, Andy]

I set "-time 2000" (the default value is 1000) and actually got more failures (25) than I did with the default setting.  If I run just the interrupt tests ("-t interrupt."), they all pass.  

-----Original Message-----
From: Aleksey Shipilev [mailto:aleksey.shipilev at gmail.com] 
Sent: Wednesday, August 10, 2016 3:54 PM
To: Johnson, Andy <johnsona at cboe.com>; 'jcstress-dev at openjdk.java.net' <jcstress-dev at openjdk.java.net>
Subject: Re: Issues running jcstress on multi-core systems

On 08/10/2016 07:41 PM, Johnson, Andy wrote:
> I have recently downloaded, built and run jcstress (custom suite only, 
> for now) on a 24-core Linux server-class system.  I am finding that 
> several of the "interrupt" tests are failing.  However, I have 
> discovered that the number of failures seems to be related to the 
> number of processor cores being used during the test.

"interrupt" tests are inherently time-based: they usually wait for timeout. There is a chance that timeout is not enough on busy machines
-- while the test tries to assert that the code quits, it runs out of time before quitting, and infra fails it.

Now, I realized we have a hard-coded timeout in the tests. Oops. Fixed, now it is derived from the iteration time:
  http://hg.openjdk.java.net/code-tools/jcstress/rev/b0c5e26af669

So, with an updated jcstress, you may want to try different "-time <msec>" settings and see if it helps. If it does help, we may need to throttle other tests while interrupt tests are executing.

> I am using "taskset" to control the number of cores used by java.

jcstress harness accepts "-sc <numCPUs>" to artificially limit the number of hardware threads to use.

Thanks,
-Aleksey