Gate DirectMemoryAntagonist.burstLoop() on governor; log throttle transitions; disable Gradle daemon in inline chaos.jar build

burstLoop() had its own fixed sleep but never checked MemoryGovernor,
letting it allocate at full rate regardless of memory pressure. Governor
now logs each throttle/release transition so CI runs show whether it
engaged. A lingering Gradle daemon from the inline chaosJar build was also
sharing the CI container's cgroup with the chaos JVM.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: jbachorik

ddprof-stresstest/src/chaos/java/com/datadoghq/profiler/chaos/DirectMemoryAntagonist.java

@@ -115,6 +115,7 @@ private void burstLoop() {
                 Thread.currentThread().interrupt();
                 return;
             }
+            MemoryGovernor.pace();
         }
         sink.addAndGet(acc);
     }

ddprof-stresstest/src/chaos/java/com/datadoghq/profiler/chaos/MemoryGovernor.java

@@ -119,14 +119,22 @@ private static void update(Path usagePath, long limitBytes) throws IOException {
 
         boolean high = cgroupFraction >= CGROUP_HIGH_WATERMARK || heapFraction >= HEAP_HIGH_WATERMARK;
         boolean low = cgroupFraction <= CGROUP_LOW_WATERMARK && heapFraction <= HEAP_LOW_WATERMARK;
-        if (high) {
+        if (high && !throttled) {
             throttled = true;
-        } else if (low) {
+            log(cgroupFraction, heapFraction, true);
+        } else if (low && throttled) {
             throttled = false;
+            log(cgroupFraction, heapFraction, false);
         }
         // else: in the dead zone between watermarks — keep current state.
     }
 
+    private static void log(double cgroupFraction, double heapFraction, boolean nowThrottled) {
+        System.out.println("[chaos] memory-governor " + (nowThrottled ? "throttling" : "released")
+                + " cgroup=" + String.format("%.2f", cgroupFraction)
+                + " heap=" + String.format("%.2f", heapFraction));
+    }
+
     private static Path firstReadable(Path[] candidates) {
         for (Path p : candidates) {
             if (Files.isReadable(p)) {

utils/run-chaos-harness.sh

@@ -110,7 +110,10 @@ fi
 CHAOS_JAR="${ROOT}/ddprof-stresstest/build/libs/chaos.jar"
 if [ ! -f "${CHAOS_JAR}" ]; then
   echo "chaos.jar not present — building inline"
-  ( cd "${ROOT}" && ./gradlew :ddprof-stresstest:chaosJar -q )
+  # --no-daemon: a lingering Gradle daemon shares this container's cgroup with
+  # the chaos JVM we're about to launch and eats into the same memory ceiling
+  # the MemoryGovernor is trying to protect.
+  ( cd "${ROOT}" && ./gradlew :ddprof-stresstest:chaosJar -q --no-daemon )
 fi
 if [ ! -f "${CHAOS_JAR}" ]; then
   echo "FAIL:chaos.jar unavailable" >&2