JEP 522 performance regression with large pages

[Thomas Schatzl]

Hi Brian,

On 28.08.25 23:49, Brian S O'Neill wrote:
> Okay...
> 
> sysctl -w vm.nr_hugepages=2048
> 
> java -XX:+UseG1GC --enable-native-access=ALL-UNNAMED --add-exports 
> java.base/jdk.internal.misc=ALL-UNNAMED --enable-native-access=ALL- 
> UNNAMED --add-opens java.base/jdk.internal.misc=ALL-UNNAMED -Xms3g - 
> Xmx3g -XX:+UseLargePages -XX:-UseTransparentHugePages <main class>
> 
> G1GC:         234.7 seconds
> G1GC JEP 522: 230.7 seconds
> 
> So, it seems that regression is with THP.

   given your report about THP issues, a colleague looked into the THP 
code, and it seems that THP is somewhat broken for JDK 25.

This is currently under investigation in 
https://bugs.openjdk.org/browse/JDK-8366434.

Not sure if it helps here, because in both baseline and changed code the 
error is probably present.

Hth,
   Thomas