Integrated: 8361376: Regressions 1-6% in several Renaissance in 26-b4 only MacOSX aarch64

[Dean Long]

On Sat, 19 Jul 2025 01:39:12 GMT, Dean Long <dlong at openjdk.org> wrote:

> This PR removes the recently added lock around set_guard_value, using instead Atomic::cmpxchg to atomically update bit-fields of the guard value.  Further, it takes a fast-path that uses the previous direct store when at a safepoint.  Combined, these changes should get us back to almost where we were before in terms of overhead.  If necessary, we could go even further and allow make_not_entrant() to perform a direct byte store, leaving 24 bits for the guard value.

This pull request has now been integrated.

Changeset: f9640398
Author:    Dean Long <dlong at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/f96403986b99008593e025c4991ee865fce59bb1
Stats:     240 lines in 15 files changed: 128 ins; 71 del; 41 mod

8361376: Regressions 1-6% in several Renaissance in 26-b4 only MacOSX aarch64

Co-authored-by: Martin Doerr <mdoerr at openjdk.org>
Reviewed-by: mdoerr, aph, eosterlund

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PR: https://git.openjdk.org/jdk/pull/26399