RFR: 8329764: G1: Handle null references during verification first

[Stefan Karlsson]

On Fri, 5 Apr 2024 11:09:17 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review this change that suggests to move the null reference check in object iteration during heap verification first.
> 
> The reason is as stated, since null references are fairly common (not only in that test mentioned in https://bugs.openjdk.org/browse/JDK-8329314), it may make sense to put it first. Also, null references never fail anyway (and verification failure is supposed to be uncommon).
> 
> Improves total runtime of that test case from 3s (~3.9s cpu time) to 2.2s (~3.1s cpu time).
> 
> If you think it makes the code too ugly, I will retract it.
> 
> Testing: gha, local testing.

I integrated the simplest version of #18595 now. I still think it would be nice to clean away the assert(_containing_obj...) with my proposed changes. Should I do that? Or do you have some other plan for it?

-------------

PR Comment: https://git.openjdk.org/jdk/pull/18650#issuecomment-2039631685