RFR: 8246494: introduce vm.flagless at-requires property

[Igor Ignatyev]

On Wed, 17 Mar 2021 00:45:00 GMT, Mikhailo Seledtsov <mseledtsov at openjdk.org> wrote:

>> resurrecting old [RFR](https://mail.openjdk.java.net/pipermail/hotspot-dev/2020-June/041981.html):
>> 
>>> Hi all,
>>> 
>>> could you please review the patch which introduces a new @requires property to filter out the tests which ignore externally provided JVM flags?
>>> 
>>> the idea behind this patch is to have a way to clearly mark tests which ignore flags, so 
>>> a) it's obvious that they don't execute a flag-guarded code/feature, and extra care should be taken to use them to verify any flag-guarded changed;
>>> b) they can be easily excluded from runs w/ flags.
>>> 
>>> @requires and VMProps allows us to achieve both, so it's been decided to add a new property `vm.flagless`. `vm.flagless` is set to false if there are any XX flags other than `-XX:MaxRAMPercentage` and `-XX:CreateCoredumpOnCrash` (which are known to be set almost always) or any X flags other `-Xmixed`; in other words any tests w/ `@requires vm.flagless` will be excluded from runs w/ any other X / XX flags passed via `-vmoption` / `-javaoption`. in rare cases, when one still wants to run the tests marked by `vm.flagless`  w/ external flags, `vm.flagless` can be forcefully set to true by setting any value to `TEST_VM_FLAGLESS` env. variable.
>>> 
>>> this patch adds necessary common changes and marks common tests, namely Scimark, GTestWrapper and TestNativeProcessBuilder. Component-specific tests will be marked separately by the corresponding subtasks of 8151707[1].
>>> 
>>> please note, the patch depends on CODETOOLS-7902336[2], which will be included in the next jtreg version, so this patch is to be integrated only after jtreg5.1 is promoted and we switch to use it by 8246387[3].
>>> 
>>> JBS: https://bugs.openjdk.java.net/browse/JDK-8246494
>>> webrev: http://cr.openjdk.java.net/~iignatyev//8246494/webrev.00
>>> testing: marked tests w/ different XX and X flags w/ and w/o TEST_VM_FLAGLESS env. var, and w/o any flags
>>> 
>>> [1] https://bugs.openjdk.java.net/browse/JDK-8151707
>>> [2] https://bugs.openjdk.java.net/browse/CODETOOLS-7902336
>>> [3] https://bugs.openjdk.java.net/browse/JDK-8246387
>>> 
>> 
>> after offline discussion with @pliden, it has been decided to reduce the scope of [8246499](https://bugs.openjdk.java.net/browse/JDK-8246499) and not mark the tests that use `UseXGC` flags for selection, e.g. `test/hotspot/jtreg/gc/z/TestSmallHeap.java`.
>> 
>> Thanks,
>> -- Igor
>
> These changes look good to me.

Thanks, Misha!

-- Igor

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PR: https://git.openjdk.java.net/jdk/pull/2800