There are various regressions in 26+27 after JDK-8371986. The list of benchmarks affected are:

Footprint3-Spring-G1 / Linux-aarch64
                                     Linux-x64
Footprint3-SwingSet-G1 / Windows-x64
JFR-Startup3-Jetty11 / Windows-x64
                                     MacOS-x64
                                     MacOS-aarch64
FR-Startup3-Noop-Base-G1 / Windows-x64
                                                MacOS-x64
SPECjvm2008-MonteCarlo-ParGC / Linux-aarch64
                                                           Linux-x64
                                                           Windows-x64
SPECjvm2008-SOR.large-ParGC / Linux-aarch64
SPECjvm2008-SOR.small-ParGC / Linux-aarch64
                                                         Linux-x64
Renaissance-FjKmeans / Linux-aarch64
                                         Linux-x64
                                         MacOS-x64

Update:
Two more benchmarks have isolated jdk-26+27-2697 (ie, JDK-8371986).

Perfstartup-Netty-G1 / Linux-aarch64
Perfstartup-SpringBoot-G1 / Linux-x64

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Some of these may have regressed as well on platforms not listed. Those results may be smaller, nosier and not definitively show the regression. The list above focuses on benchmarks configs that were able to isolated to JDK-8371986.