# HG changeset patch
# User wenzelm
# Date 1742470787 -3600
# Node ID 1a4be2516f5003f9e40ed8af7d6bde6689f34164
# Parent  3529946fca19c7409cfb26781da7eaf10b8c1e70
ZGC of Java 21 is enabled by default: now possible, because Windows Server 2012 (vmnipkow9) has been discontinued;
enforce rebuild of Isabelle/ML and Isabelle/Scala;

diff -r 3529946fca19 -r 1a4be2516f50 Admin/components/README.md
--- a/Admin/components/README.md	Wed Mar 19 22:18:52 2025 +0000
+++ b/Admin/components/README.md	Thu Mar 20 12:39:47 2025 +0100
@@ -47,6 +47,7 @@
       - macOS 15 Sequoia (untested)
 
   * `x86_64-windows`
+      - Windows Server 2019 (minimum for Java ZGC)
       - **Windows Server 2022** (`se0.proof.cit.tum.de`)
       - **Windows 10**
       - Windows 11
diff -r 3529946fca19 -r 1a4be2516f50 NEWS
--- a/NEWS	Wed Mar 19 22:18:52 2025 +0000
+++ b/NEWS	Thu Mar 20 12:39:47 2025 +0100
@@ -112,6 +112,11 @@
 
 *** System ***
 
+* The Z Garbage Collector (ZGC) of Java 21 is now used by default (see
+also https://wiki.openjdk.org/display/zgc). This should work uniformly
+on all platforms, but requires a reasonably new version of Windows
+(Windows 10 or Windows Server 2019).
+
 * SSH connections allow both bash and zsh as remote shell. This is
 particularly important for macOS, where zsh is the default user shell.
 
diff -r 3529946fca19 -r 1a4be2516f50 etc/settings
--- a/etc/settings	Wed Mar 19 22:18:52 2025 +0000
+++ b/etc/settings	Thu Mar 20 12:39:47 2025 +0100
@@ -12,7 +12,7 @@
 ### Isabelle/Scala
 ###
 
-ISABELLE_JAVA_SYSTEM_OPTIONS="-server -Dfile.encoding=UTF-8 -Disabelle.threads=0"
+ISABELLE_JAVA_SYSTEM_OPTIONS="-server -Dfile.encoding=UTF-8 -Disabelle.threads=0 -XX:+UseZGC -XX:+ZGenerational"
 
 ISABELLE_TOOL_JAVA_OPTIONS="-Djava.awt.headless=true -Xms512m -Xmx4g -Xss16m"
 
diff -r 3529946fca19 -r 1a4be2516f50 src/Pure/ROOT.ML
--- a/src/Pure/ROOT.ML	Wed Mar 19 22:18:52 2025 +0000
+++ b/src/Pure/ROOT.ML	Thu Mar 20 12:39:47 2025 +0100
@@ -1,6 +1,6 @@
 (*  Title:      Pure/ROOT.ML
     Author:     Makarius
-    UUID:       26c42c05-587c-41c1-882d-903627102706
+    UUID:       619a7a37-9241-410f-82a1-be35d8c9e937
 
 Main entry point for the Isabelle/Pure bootstrap process.
 
diff -r 3529946fca19 -r 1a4be2516f50 src/Pure/ROOT.scala
--- a/src/Pure/ROOT.scala	Wed Mar 19 22:18:52 2025 +0000
+++ b/src/Pure/ROOT.scala	Thu Mar 20 12:39:47 2025 +0100
@@ -1,6 +1,6 @@
 /*  Title:      Pure/ROOT.scala
     Author:     Makarius
-    UUID:       26c42c05-587c-41c1-882d-903627102706
+    UUID:       619a7a37-9241-410f-82a1-be35d8c9e937
 
 Root of isabelle package.
 */