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

David Holmes david.holmes at oracle.com
Tue Jun 5 23:04:56 UTC 2018

On 6/06/2018 7:09 AM, coleen.phillimore at oracle.com wrote:
> 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 for the review Coleen! Yes I'm glad it was just a 
misunderstanding on my part.


> 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

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