RFR: 8338856: [BACKOUT] JDK-8337828: CDS: Trim down minimum GC region alignment

[Aleksey Shipilev]

On Thu, 22 Aug 2024 17:28:56 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This reverts commit 598169756c903bb1f77e35ea32717043bc166e3c.
> 
> Causes failures in deeper testing, see [JDK-8338753](https://bugs.openjdk.org/browse/JDK-8338753). I missed it, because my testing did not run with `-XX:-UseCompressedOops`. The test with many classes fails readily with this flag:
> 
> 
> $ CONF=linux-x86_64-server-fastdebug make test TEST=runtime/cds/appcds/LotsOfClasses.java TEST_VM_OPTS=-XX:-UseCompressedOops
> 
> java.lang.RuntimeException: Hotspot crashed
> at jdk.test.lib.cds.CDSTestUtils.executeAndLog(CDSTestUtils.java:699)
> at jdk.test.lib.cds.CDSTestUtils.executeAndLog(CDSTestUtils.java:675)
> at jdk.test.lib.cds.CDSTestUtils.createArchive(CDSTestUtils.java:270)
> at jdk.test.lib.cds.CDSTestUtils.createArchiveAndCheck(CDSTestUtils.java:306)
> at LotsOfClasses.main(LotsOfClasses.java:56)
> at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
> at java.base/java.lang.reflect.Method.invoke(Method.java:573)
> at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:333)
> at java.base/java.lang.Thread.run(Thread.java:1575)
> 
> 
> This is really a VM bug that we crash and not exit nicely, but with the old value we are "lucky" these many classes still fit into 1M array. Backout to return to that point would do for now.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `runtime/cds`
>  - [x] Linux x86_64 server fastdebug, `runtime/cds` with `-XX:-UseCompressedOops`

Most platforms are fine. I am not going to wait for slower MacOS instances.

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PR Comment: https://git.openjdk.org/jdk/pull/20681#issuecomment-2305511956