Add Whitebox check for host cpu

Author: jerboaa

src/hotspot/share/prims/whitebox.cpp

@@ -158,6 +158,13 @@ class VM_WhiteBoxOperation : public VM_Operation {
   bool allow_nested_vm_operations() const        { return true; }
 };
 
+#ifdef LINUX
+class Whitebox_Linux : public os::Linux {
+ public:
+  static int host_cpus() { return os::Linux::active_processor_count(); }
+};
+#endif
+
 
 WB_ENTRY(jlong, WB_GetObjectAddress(JNIEnv* env, jobject o, jobject obj))
   return (jlong)(void*)JNIHandles::resolve(obj);
@@ -2488,6 +2495,12 @@ WB_ENTRY(jint, WB_ValidateCgroup(JNIEnv* env,
   return ret;
 WB_END
 
+// Physical cpus of the host machine (including containers), Linux only.
+WB_ENTRY(jint, WB_HostCPUs(JNIEnv* env, jobject o))
+  LINUX_ONLY(return Whitebox_Linux::host_cpus();)
+  return -1; // Not used/implemented on other platforms
+WB_END
+
 WB_ENTRY(void, WB_PrintOsInfo(JNIEnv* env, jobject o))
   os::print_os_info(tty);
 WB_END
@@ -2929,6 +2942,7 @@ static JNINativeMethod methods[] = {
                                                       (void*)&WB_ValidateCgroup },
   {CC"hostPhysicalMemory",        CC"()J",            (void*)&WB_HostPhysicalMemory },
   {CC"hostPhysicalSwap",          CC"()J",            (void*)&WB_HostPhysicalSwap },
+  {CC"hostCPUs",                  CC"()I",            (void*)&WB_HostCPUs },
   {CC"printOsInfo",               CC"()V",            (void*)&WB_PrintOsInfo },
   {CC"disableElfSectionCache",    CC"()V",            (void*)&WB_DisableElfSectionCache },
   {CC"resolvedMethodItemsCount",  CC"()J",            (void*)&WB_ResolvedMethodItemsCount },

test/hotspot/jtreg/containers/systemd/SystemdMemoryAwarenessTest.java

@@ -27,26 +27,38 @@
  * @summary Memory/CPU awareness test for JDK-under-test inside a systemd slice.
  * @requires systemd.support
  * @library /test/lib
- * @build HelloSystemd
- * @run driver SystemdMemoryAwarenessTest
+ * @build HelloSystemd jdk.test.whitebox.WhiteBox
+ * @run driver jdk.test.lib.helpers.ClassFileInstaller -jar whitebox.jar jdk.test.whitebox.WhiteBox
+ * @run main/othervm -Xbootclasspath/a:whitebox.jar -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI SystemdMemoryAwarenessTest
  */
 import java.nio.file.Files;
 import java.nio.file.NoSuchFileException;
+import jdk.test.whitebox.WhiteBox;
 import jdk.test.lib.containers.systemd.SystemdRunOptions;
 import jdk.test.lib.containers.systemd.SystemdTestUtils;
 import jdk.test.lib.containers.systemd.SystemdTestUtils.ResultFiles;
 
 
 public class SystemdMemoryAwarenessTest {
 
+    private static final WhiteBox wb = WhiteBox.getWhiteBox();
+
     public static void main(String[] args) throws Exception {
        testHelloSystemd();
     }
 
     private static void testHelloSystemd() throws Exception {
         SystemdRunOptions opts = SystemdTestUtils.newOpts("HelloSystemd");
-        // 1 GB memory and 2 cores CPU
-        opts.memoryLimit("1000M").cpuLimit("200%");
+        // 1 GB memory
+        opts.memoryLimit("1000M");
+        int physicalCpus = wb.hostCPUs();
+        if (physicalCpus < 3) {
+           System.err.println("WARNING: host system only has " + physicalCpus + " expected >= 3");
+        }
+        // 1 or 2 cores limit depending on physical CPUs
+        int coreLimit = Math.min(physicalCpus, 2);
+        System.out.println("DEBUG: Running test with a CPU limit of " + coreLimit);
+        opts.cpuLimit(String.format("%d%%", coreLimit * 100));
         opts.sliceName(SystemdMemoryAwarenessTest.class.getSimpleName());
 
         ResultFiles files = SystemdTestUtils.buildSystemdSlices(opts);
@@ -55,7 +67,7 @@ private static void testHelloSystemd() throws Exception {
             SystemdTestUtils.systemdRunJava(opts)
                 .shouldHaveExitValue(0)
                 .shouldContain("Hello Systemd")
-                .shouldContain("OSContainer::active_processor_count: 2")
+                .shouldContain("OSContainer::active_processor_count: " + coreLimit)
                 .shouldContain("Memory Limit is: 1048576000"); // 1 GB
         } finally {
             try {

test/lib/jdk/test/whitebox/WhiteBox.java

@@ -764,6 +764,7 @@ public native int validateCgroup(String procCgroups,
   public native void printOsInfo();
   public native long hostPhysicalMemory();
   public native long hostPhysicalSwap();
+  public native int hostCPUs();
 
   // Decoder
   public native void disableElfSectionCache();