On Wed, 23 Oct 2024 18:14:50 GMT, Martin Doerr <mdo...@openjdk.org> wrote:
> This code causes test errors in `CompressedClassPointersEncodingScheme.java` > on s390 and PPC64. It forces the shift to `log_cacheline` which is 7 on PPC64 > and 9 on s390. The test passes when we remove "s > log_cacheline && " from > the condition below. It's a bit late. We are close to pushing. While it should be harmless to drop below alignment to below cache line size, this would be a change affecting all platforms and would require all tests repeated. PPC/s390 are not targeted by the JEP. There had never been a discussion I am aware of that these platforms have to be clean with +COH. While it's nice that the changes had been contributed, I don't think that test errors on these platforms should hold up pushing this RFE. Therefore, if needed, we should just omit +COH part of the test for PPC/S390. But then, what exactly is the error? If it's just the test assuming that cache line size is log 6, then the test should be fixed for ppc, not hotspot. > In addition, it doesn't fit to the comment which claims we should avoid > shifts larger than the cacheline size. This enforces shifts to be larger (or > equal to) than the cacheline size. ?? The comment is correct. We try to avoid hyper alignment, hence we drop the shift to - if possible - log 2 cache line size. If it's equal to log 2 cache line size, we succeeded. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1814598543
