RFR: 8354145: G1: UseCompressedOops boundary is calculated on maximum heap region size instead of maxiumum ergonomic heap region size [v4]
duke
duke at openjdk.org
Wed Apr 30 03:31:48 UTC 2025
On Tue, 15 Apr 2025 03:31:48 GMT, Tongbao Zhang <duke at openjdk.org> wrote:
>> After [JDK-8275056](https://bugs.openjdk.org/browse/JDK-8275056), The max heap region size became 512M, and the calculation of CompressedOops based on the max_heap_size - max_heap_region_size.
>> So before this patch, the CompressedOops will turn on below 32G - 32m, After this patch is 32G -512m.
>>
>> When our Apps migrating from JDK11 to JDK21, the heap size parameters(Xmx32736m) will turn off the CompressedOops.
>>
>> Since the current max ergonomics size is still 32m, We hoped that the original behavior will not be changed if HeapRegionSize is not explicitly set.
>>
>> before this patch:
>>
>> ./build/linux-x86_64-server-release/images/jdk/bin/java -Xmx32736m -XX:+PrintFlagsFinal -version | grep CompressedOops
>> bool UseCompressedOops = false {product lp64_product} {default}
>> openjdk version "25-internal" 2025-09-16
>> OpenJDK Runtime Environment (build 25-internal-adhoc.root.jdk)
>> OpenJDK 64-Bit Server VM (build 25-internal-adhoc.root.jdk, mixed mode, sharing)
>>
>>
>> after this patch:
>>
>> ./build/linux-x86_64-server-release/images/jdk/bin/java -Xmx32736m -XX:+PrintFlagsFinal -version | grep CompressedOops
>> bool UseCompressedOops = true {product lp64_product} {ergonomic}
>> openjdk version "25-internal" 2025-09-16
>> OpenJDK Runtime Environment (build 25-internal-adhoc.root.jdk)
>> OpenJDK 64-Bit Server VM (build 25-internal-adhoc.root.jdk, mixed mode, sharing)
>
> Tongbao Zhang has updated the pull request incrementally with one additional commit since the last revision:
>
> typo
@tbzhang
Your change (at version 17c0a8a03e4577fed20c40bb1f209c017522ffbc) is now ready to be sponsored by a Committer.
-------------
PR Comment: https://git.openjdk.org/jdk/pull/24541#issuecomment-2840710313
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