Status of JEP-8204088/JDK-8236073

[Thomas Schatzl]

Hi Rodrigo,

On 18.08.21 09:36, Rodrigo Bruno wrote:
> Hi Thomas, Hi Man,
> 
> On Mon, 2 Aug 2021 at 16:49, Thomas Schatzl <thomas.schatzl at oracle.com 
> <mailto:thomas.schatzl at oracle.com>> wrote:
[...]
> 
>     Fwiw, these two are fairly independent issues, and the main problem
>     with
>     the proposed CurrentMaxHeapSize patch has been that the change is not
>     atomic in the sense that the changes simply modify the global heap size
>     variable without regard whether and when it is accessed. That may
>     result
>     in fairly nasty races as different components of the GC may then have a
>     different notion of what the current max heap size actually is at the
>     moment.
> 
> 
> That is true. However, we could easily do the update to 
> CurrentMaxHeapSize inside a VMOperation to ensure an atomic change. This 
> is not in the current patch but it is probably a simple change. Right?

Unfortunately, not, at least when I looked last time. There did not seem 
to be a way to trigger a VM operation based on the change of a variable 
using a jcmd command.

An intermediate step of just polling that variable (in a g1 service 
task) and then triggering it or just waiting until the next gc (which is 
probably best, particular wrt to decreases in heap size) could be options.

Thanks,
   Thomas