"incompatible property" error when using --add-modules, --add-opens, --add-exports, etc.

[ioi.lam at oracle.com]

Yes, this is expected behavior.

A short explanation: the Leyden optimizations depends on 
-XX:+AOTClassLinking, which requires that all classes loaded during the 
training run are visible during the production run.

For example, if --add-module is specified differently during the two 
runs, class A could be loading in the training run and become inlined by 
AOT-compiled methods. At runtime, if a different set of --add-modules is 
used, class A may not be loadable, and we would have to invalidate the 
corresponding optimizations.

Doing such checks correctly is complicated. Today, we have a very simple 
check -- (a) the full module graph must be archived during the training 
run, and (b) the full module graph must be loaded from the AOT cache 
during the production run. This way we know the exact set of modules are 
used in the two runs so the same set of classes are visible.

Currently, we allow the full module graph to be archived only with a 
restricted set of options -- see 
ModuleBootstrap::canUseArchivedBootLayer(). We are working to relax the 
restrictions (see https://bugs.openjdk.org/browse/JDK-8328313 -- 
Archived module graph should allow identical --module-path to be 
specified during dump time and run time).

Supporting --add-modules, --add-opens, and --add-exports may require 
more work. For --add-opens and --add-exports, I'd to understand why they 
are being used. Maybe they are for accessing JDK internals that 
otherwise shouldn't really be touched?

Thanks

- Ioi


On 9/9/24 1:16 PM, Boyce, Jeffrey wrote:
> Hello,
> I am attempting to evaluate performance improvements afforded by the 
> Leyden CDS enhancements for an embedded application running on 
> aarch64.  The application makes extensive use of the --add-modules, 
> --add-opens, and --add-exports command line arguments. However, it 
> appears that these arguments are incompatible with the 
> -XX:CacheDataStore option, as their use results in errors similar to 
> the following:
> [0.004s][warning][cds] optimized module handling/full module graph: 
> disabled due to incompatible property: 
> jdk.module.addopens=java.base/java.nio=org.apache.tomcat.embed.core
> Error occurred during initialization of VM
> CacheDataStore cannot be created because AOTClassLinking is enabled 
> but full module graph is disabled
> Is this the expected behavior?  If yes, is there a workaround or a 
> plan to support these options in the future?
> Thanks,
> Jeff Boyce
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/leyden-dev/attachments/20240909/6913a64b/attachment.htm>