RFR (S): 7129271 G1: Interference from multiple threads in PrintGC/PrintGCDetails output

[John Cuthbertson]

Hi Tony,

Thanks. Good point. I missed the print_heap_after_gc() call. Consider it 
done.

JohnC

On 01/13/12 09:25, Tony Printezis wrote:
> John,
>
> Thanks for taking into account my feedback! My only comment is that 
> you should maybe move the doConcurrentMark() call to even further down 
> (i.e., as the last thing we do in that method before return true;) 
> given that there's still some output that can be generated after its 
> current location (e.g., PrintHeapAtGC).
>
> Tony
>
> On 01/13/2012 12:11 PM, John Cuthbertson wrote:
>> Hi Everyone,
>>
>> Based upon feedback from Tony, I have a much simpler version of this 
>> change. The new changes can be found at: 
>> http://cr.openjdk.java.net/~johnc/7129271/webrev.1/
>>
>> Thanks,
>>
>> JohnC
>>
>> On 01/12/12 11:28, John Cuthbertson wrote:
>>> Hi Everyone,
>>>
>>> Can I have a couple of volunteers review the changes for this CR? 
>>> The webrev can be found at: 
>>> http://cr.openjdk.java.net/~johnc/7129271/webrev.0/
>>>
>>> The issue was that the when PrintGC or PrintGCDetails was enabled, 
>>> during an initial pause, the "concurrent-mark-start" message from 
>>> the ConcurrentMark thread was interfering with the output (by the VM 
>>> thread) from the GC pause. This was adding a randomness and 
>>> irregularity to the output that was making it difficult to parse. It 
>>> was also seen more frequently when the GC logging output was 
>>> directed to a file rather than stdout.
>>>
>>> The solution is to move the code that signals the Concurrent Mark 
>>> thread to after when the output from the GC pause is complete.
>>>
>>> In the webrev, please ignore the counts of the number of lines 
>>> changed. I added an inner scope and so indented a bunch of code 
>>> which I think has confused the webrev tool. Fortunately the actual 
>>> web diffs seem to have not included the extra whitespace.
>>>
>>> Testing: the GC test suite (with a low marking threshold - 2% to 
>>> create lots of marking cycles)
>>>
>>> Thanks,
>>>
>>> JohnC
>>>
>>>
>>