RFR: 8268573: Remove expired flags in JDK 19

[Alan Bateman]

On Tue, 14 Dec 2021 12:47:34 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> src/hotspot/share/runtime/arguments.cpp line 551:
>> 
>>> 549:   { "G1RSetSparseRegionEntries",    JDK_Version::undefined(), JDK_Version::jdk(18), JDK_Version::jdk(19) },
>>> 550:   { "AlwaysLockClassLoader",        JDK_Version::jdk(17), JDK_Version::jdk(18), JDK_Version::jdk(19) },
>>> 551:   { "UseBiasedLocking",             JDK_Version::jdk(15), JDK_Version::jdk(18), JDK_Version::jdk(19) },
>> 
>> There are a number of servers with start scripts that specify -XX:-UseBiasedLocking. The option may be obsolete and I wonder if better to leave it as obsolete until there is more uptake of JDK 17 which does not need to disable it explicitly.
>
> I don't understand the relevance of "uptake of JDK 17" - this change only affects 19. Anyone on 17 will get the deprecation warning as we deliberately deferred obsoleting the flag until JDK 18.

It means the start scripts won't be usable with JDK 19+ builds so it complicates testing with those servers. Once these servers get to JDK 17 (actually JDK 15+) then they should be able to drop this option. I think the more general point is that we could be less aggressive about removing obsolete VM options when we know they are being used. In the past, the PermGen options were left as obsolete options for a long time because there were widely used.

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PR: https://git.openjdk.java.net/jdk/pull/6819