Add jdk28-zgc: ZGC startup and warmup baseline on JDK 25/27/28-ea, and a probe for JEP 545/546

Spring Boot 4.1.1 harness measuring first-response time versus initial heap size and a 20,000-request warmup. Shows -XX:+ZAdaptiveHeapSizing is not yet in any build. Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01WzVQ6zFh9cuLPj9RSbRH8U
2026-10-12 17:13:14 +00:00
parent 2f88734f5d
commit df13a904d7
11 changed files with 431 additions and 0 deletions
@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+# Regenerates every file in output/. Set J25, J27, J28 to the three JDK home directories.
+# Timing results drift between runs and machines; treat them as indicative, not exact.
+set -u
+HERE="$(cd "$(dirname "$0")" && pwd)"
+OUT="$HERE/../output"; mkdir -p "$OUT"
+: "${J25:?}" "${J27:?}" "${J28:?}"
+export JDK_CLIENT="$J25"
+RUNS=${RUNS:-5}
+
+# 01 - what does each JDK say about the ZGC flags the two JEPs talk about?
+{
+  for p in "25|$J25" "27|$J27" "28-ea|$J28"; do
+    v=${p%%|*}; h=${p#*|}
+    echo "== JDK $v"
+    "$h/bin/java" -version 2>&1 | grep -v Picked | sed -n 1p
+    "$h/bin/java" -XX:+UnlockExperimentalVMOptions -XX:+UseZGC -XX:+PrintFlagsFinal -version 2>&1 \
+      | grep -E ' (InitialHeapSize|MaxHeapSize|SoftMaxHeapSize|ZUncommit|ZUncommitDelay) ' | sed 's/ \{2,\}/ /g'
+    echo "-- probing -XX:+ZAdaptiveHeapSizing"
+    "$h/bin/java" -XX:+UseZGC -XX:+ZAdaptiveHeapSizing -version 2>&1 | grep -v Picked | sed -n 1p
+    echo
+  done
+} > "$OUT/01-flag-probe.txt"
+
+# 02 - startup versus initial heap size
+{
+  for p in "jdk25|$J25" "jdk27|$J27" "jdk28ea|$J28"; do
+    l=${p%%|*}; h=${p#*|}
+    "$HERE/startup.sh" "$h" "$l zgc default"      "$RUNS" -XX:+UseZGC
+    "$HERE/startup.sh" "$h" "$l zgc Xms64m"       "$RUNS" -XX:+UseZGC -Xms64m
+    "$HERE/startup.sh" "$h" "$l zgc Xms1g"        "$RUNS" -XX:+UseZGC -Xms1g
+    "$HERE/startup.sh" "$h" "$l zgc Xms3g"        "$RUNS" -XX:+UseZGC -Xms3g
+    "$HERE/startup.sh" "$h" "$l zgc Xms3g pretouch" "$RUNS" -XX:+UseZGC -Xms3g -XX:+AlwaysPreTouch
+  done
+} > "$OUT/02-startup-vs-xms.txt" 2>&1
+
+# 03 - warmup: how long do the first 20,000 requests take?
+{
+  for p in "jdk25|$J25" "jdk28ea|$J28"; do
+    l=${p%%|*}; h=${p#*|}
+    "$HERE/warmup.sh" "$h" "$l zgc default"  -XX:+UseZGC
+    "$HERE/warmup.sh" "$h" "$l zgc Xms3g"    -XX:+UseZGC -Xms3g
+    "$HERE/warmup.sh" "$h" "$l zgc Xms64m"   -XX:+UseZGC -Xms64m
+  done
+} > "$OUT/03-warmup.txt" 2>&1