RFR: 8214858: Improve module graph archiving

Claes Redestad claes.redestad at oracle.com
Thu Dec 6 12:03:22 UTC 2018

Jiangli, Alan,

thanks for reviewing!

On 2018-12-06 09:56, Alan Bateman wrote:
> On 05/12/2018 15:13, Claes Redestad wrote:
>> Hi,
>> a few improvements to how we archive module graph information:
>> - archive an instance of ArchiveModuleGraph rather than individual 
>> fields
>> - archiving the exportedPackagesToOpen and concealedPackagesToOpen 
>> maps improve sharing and substantially reduce bytecode executed (~30k)
>> - archiving the remaining flags in the ArchivedModuleGraph means we 
>> no longer need to archive SystemModules
>>   - this means we no longer load jdk.internal.module.SystemModules 
>> and jdk.internal.module.SystemModules$default at runtime
>> - for robustness ensure we either resolve either everything or 
>> nothing from the archive (there are some overlapping safeguards here, 
>> e.g., CDS is disabled when you run with --limit-modules, but helps to 
>> be explicit)
>> Bugs: https://bugs.openjdk.java.net/browse/JDK-8214858
>> Webrev: http://cr.openjdk.java.net/~redestad/8214858/jdk.00/
>> Testing: tier1-3, locally tested all module and CDS tests
>> Startup tests verify a small speedup on my test setups (around -0.5ms 
>> on average)
> I think these changes look okay.
> Once we get to the point of not permitting illegal access by default 
> then we might look at this again as the concealed/exported maps won't 
> be needed for the default case. 

Yes, I can think of a few ways to simplify once --illegal-access=deny 
becomes default (and either way that will be beneficial to startup time).


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