RFR: 8262099: jcmd VM.metaspace should report unlimited size if MaxMetaspaceSize isn't specified [v2]

[Thomas Stuefe]

On Mon, 22 Feb 2021 05:47:58 GMT, Yang Yi <github.com+5010047+kelthuzadx at openjdk.org> wrote:

>> Hi,
>> 
>> Can I have a review of this minor fix about `jcmd VM.metaspace`?
>> 
>> When MaxMetaspaceSize is not specified, it would set to max_uintx, jcmd VM.metaspace reports metaspace summary information as follows:
>> 
>> $ ./jcmd <pid> VM.metaspace | grep MaxMetaspaceSize
>> MaxMetaspaceSize: 17179869184.00 GB
>> 
>> Actually, this is a bug, the expected output should be:
>> 
>> MaxMetaspaceSize: unlimited
>> 
>> The root cause of the problem is that the MaxMetaspaceSize rounding performed during arguments parsing is inconsistent with the round checking in print_settings(metaspaceRerporter.cpp).
>
> Yang Yi has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remain unchanged SAP copyright year, only update Oracle copyright year

Change looks fine, thanks for fixing. Can you please add a comment like "see Metaspace::ergo_initialize()" ?

I think the only reason we align MaxMetaspaceSize down is to forestall any comparison overflows on metaspace expansion. But I am not sure this is even an issue. I would like a solution where we leave it at max_uint and check the comparisons for overflow instead. But this patch looks fine.

Make sure you run the associated JTreg test.

Cheers, Thomas

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Marked as reviewed by stuefe (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2671