RFR: 8277854: The upper bound of GCCardSizeInBytes should be limited to 512 for 32-bit platforms

Jie Fu jiefu at openjdk.java.net
Fri Nov 26 06:37:19 UTC 2021


Hi all,

runtime/CommandLine/OptionsValidation/TestOptionsWithRanges.java crashes on linux/x86_32 with `-XX:GCCardSizeInBytes=1024`.

This is because if`-XX:GCCardSizeInBytes=1024` then `BOTConstants::N_words` [1] would be 256.
Then the guarantee [2] always fails due to _bot->offset_array(start_card), which is a u_char value, never equals to 256.

So for 32-bit platforms, the upper bound of `GCCardSizeInBytes` should be limited to 512.

Thanks.
Best regards,
Jie

[1] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/gc/shared/blockOffsetTable.cpp#L45
[2] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/gc/g1/g1BlockOffsetTable.cpp#L186

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Commit messages:
 - 8277854: The upper bound of GCCardSizeInBytes should be limited to 512 for 32-bit platforms

Changes: https://git.openjdk.java.net/jdk/pull/6569/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6569&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277854
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6569.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6569/head:pull/6569

PR: https://git.openjdk.java.net/jdk/pull/6569


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