A question about the present condition/plans of Dynamic Max Memory Limit

[Thomas Schatzl]

Hi,

On 02.02.23 08:21, Katsutomo Sekiguchi (Fujitsu) wrote:
> Dear Thomas Schatzl,
> 
> I'm interested in JEP-8204088.
> Let me ask you two questions.
> 
> First, according to "RFR-8204088: Dynamic Max Memory Limit" (*1), I believe that there is the JEP-8204088 implementation in (*2) as modified files.
> So, max_heap_size and Java.lang.Runtime#maxMemory() are implemented to adopt CurrentMaxHeapSize. However, it is not known where CurrentMaxHeapSize will be updated, and it does not appear to be implemented yet.
> Where can I find the latest implementation of JEP-8204088?
> 
> *1: https://mail.openjdk.org/pipermail/hotspot-gc-dev/2018-June/022454.html
> *2: http://cr.openjdk.java.net/~tschatzl/jelastic/cmx/
> 

The latest known, open patch is at your link [2].

> Second, could you tell me more specifically about your future plans for JEP-8204088?
> So, are there any technical barriers?

Nobody has proposed a patch that can be discussed further.

There has been additional discussion about a more encompassing proposal 
from J. Joo on this list[A], with Dynamic Max Memory Limit being a part.

As a response of mine[B] indicates ("From what I understand the main 
issue is thinking about and defining interaction with existing 
Min/Initial/MaxHeapSize flags (e.g. [1]).

SoftMaxHeapSize otherwise seems to be relatively unproblematic.

Iirc specifically for the Current/HardMaxHeapSize flag, the
implementation needs to be thought through in more detail. There is an
initial list of problems ([2]) that should be worked through and defined
as it has much more external impact.")

There are no particular technical problems, but nobody has stepped up to 
actually tackle them as far as I am aware. Contributions are welcome :)

Hth,
   Thomas

[A] 
https://mail.openjdk.org/pipermail/hotspot-gc-dev/2022-September/040096.html
[B] 
https://mail.openjdk.org/pipermail/hotspot-gc-dev/2022-September/040207.html