RFR: 8241361: ZGC: Implement memory related JFR events

[Per Liden]

On 3/30/20 5:32 PM, Stefan Karlsson wrote:
> Updated webrevs:
>   https://cr.openjdk.java.net/~stefank/8241361/webrev.04.delta/
>   https://cr.openjdk.java.net/~stefank/8241361/webrev.04/
> 
> Changes after some testing and discussions with Per:
> 
> 1) For some reason it's required by JFR testing that the .jfc files list 
> the stackTrace value. Fixed that.
> 2) Only generate ZUncommit when we actually have uncommitted memory.
> 3) Send relocation set group events for large pages.
> 4) Turn off both logging and event generation when medium pages have 
> been disabled.

Looks good!

/Per

> 
> Thanks,
> StefanK
> 
> On 2020-03-20 14:43, Stefan Karlsson wrote:
>> Hi all,
>>
>> Please review this patch to add some memory related JFR events to ZGC.
>>
>> https://cr.openjdk.java.net/~stefank/8241361/webrev.01/
>> https://bugs.openjdk.java.net/browse/JDK-8241361
>>
>> Added events:
>>
>> ZAllocationStall - Record when we run out of heap memory and the Java 
>> threads stall, waiting for the GC to free up memory.
>>
>> ZPageAllocation - Updated the existing event to also record the 
>> duration of the event. Updated the event to only be reported if the 
>> allocation takes longer than 1 ms.
>>
>> ZPageCacheFlush - Record when the page cache needs to be flushed. This 
>> usually happens when we run out of a specific page size and have to 
>> detach the physical and virtual memory to materialize a new ZPage. We 
>> also flush pages when we uncommit memory.
>>
>> ZRelocationSet - Record information about the selected relocation set.
>>
>> ZUncommit - Record when we uncommit and hand back memory to the OS.
>>
>> The patch also contains some small cosmetic changes to existing 
>> events, whitespace fixes.