RFR (S): 8174734: Safepoint sync time did not increase

[coleen.phillimore at oracle.com]

Hi, This test rewrite looks good.  I'm glad there wasn't an underlying 
bug in the time reporting code.  Thank you for fixing this.

Thanks,
Coleen

On 6/5/18 5:44 AM, David Holmes wrote:
> Bug: https://bugs.openjdk.java.net/browse/JDK-8174734
> webrev: http://cr.openjdk.java.net/~dholmes/8174734/webrev/
>
> This is a simple logic flaw in a test that expected to see the 
> safepoint sync time always increase but that's not the case because it 
> only has millisecond resolution and only measures the time taken to 
> reach a safepoint (not the time consumed by the safepoint)..
>
> This was originally fixed by Coleen:
>
> http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2018-February/026138.html 
>
>
> but I was confused as to what was actually happening and so took it 
> over. I decided to rewrite the test to actually check what can be 
> relied upon:
>  - safepoint counts and times are always positive
>  - safepoint counts are accurate (at least as many as expected)
>  - safepoint time never goes backwards
>
> Testing:
>   - running the test 50 times on each platform (across a range of 
> machines) to see if we've ironed out the intermittent failures
>
> Thanks,
> David