RFR: 8330171: Lazy W^X switch implementation

[Andrew Haley]

On Sat, 13 Apr 2024 18:16:21 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> I have one question, and I'm sorry if it has been answered before. How expensive is changing the mode? Is it just a status variable in user-space pthread lib? Or does it need a system call?
> 
> In other words, how fine granular can we get without incurring too high a cost?

It's expensive. We've seen it cause significant slowdowns in Java->VM transitions.

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PR Comment: https://git.openjdk.org/jdk/pull/18762#issuecomment-2053734174