RFR: 8241361: ZGC: Implement memory related JFR events

[Erik Österlund]

Hi Stefan,

Very nice. I like the new syntax for filling in event data and committing.
Looks good.

Thanks,
/Erik

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.