RFR: 8204554: JFR TLAB tracing broken after 8202776

[Roman Kennke]

Hi Erik,

> The recent allocation path modularization (8202776) broke JFR TLAB
> sampling. This was discovered in tier 5 testing.
> 
> The problem is that there was previously an early exit TLAB path, that
> should not run the tracing code when not returning NULL, and a
> mem_allocate call that should run the tracing code when not returning
> NULL. However, these paths were joined in a virtual member function,
> making them look the same to the tracing code, which caused the non-TLAB
> tracing code to be run on TLAB allocations as well.
> 
> The solution I propose is to move the TLAB tracing code into the new
> virtual member function. It seems that whatever GC overrides this code,
> should also decide what to do about the tracing code there anyway.
> 
> Webrev:
> http://cr.openjdk.java.net/~eosterlund/8204554/webrev.00/
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8204554
> 
> I have run failing tests locally to verify they have been fixed with the
> proposed patch. I am now running hs-tier1-3 as well, but am waiting for
> the results.

This looks good to me. Thank you!

Roman