RFR: 8319801: Recursive lightweight locking: aarch64 implementation

[Andrew Haley]

On Wed, 15 Nov 2023 09:57:40 GMT, Andrew Haley <aph at openjdk.org> wrote:

> We have found on some hardware the LSE instructions have terrible performance in the un-contended case.

Thinking about this some more, it's a very bad situation. In general, across the whole JVM, when we're doing a CAS we don't know if contention is likely. GCC/glibc make the guess that it's probably best always to use the LSE instructions. We do the same thing. Any implementation which implements LSE badly in the uncontended fast path is going to suffer.

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PR Comment: https://git.openjdk.org/jdk/pull/16608#issuecomment-1812793921