RFR: 8205928 - [TESTBUG]: jdk/internal/platform/docker/TestDockerMemoryMetrics.java fails depending on kernel config

[Bob Vandette]

Please review this small fix to correct a test failure when the Linux system kernel is
not configured with the CONFIG_MEMCG_KMEM option.

The Container Metric tests are dependent on docker which allow us to assume a certain minimum
Linux kernel configuration level. However, the kernel memory resource limiting feature is not a hard
requirement for docker. This test will need to be updated to allow for running on kernels without this
option.  A 0 return from the getKernelMemoryLimit is defined to indicate that this API is not available.

BUG: https://bugs.openjdk.java.net/browse/JDK-8205928

PROPOSED FIX:

diff --git a/test/jdk/jdk/internal/platform/docker/MetricsMemoryTester.java b/test/jdk/jdk/internal/platform/docker/MetricsMemoryTester.java
--- a/test/jdk/jdk/internal/platform/docker/MetricsMemoryTester.java
+++ b/test/jdk/jdk/internal/platform/docker/MetricsMemoryTester.java
@@ -95,10 +95,11 @@
 
     private static void testKernelMemoryLimit(String value) {
         long limit = getMemoryValue(value);
-        if (limit != Metrics.systemMetrics().getKernelMemoryLimit()) {
+        long kmemlimit = Metrics.systemMetrics().getKernelMemoryLimit();
+        if (kmemlimit != 0 && limit != kmemlimit) {
             throw new RuntimeException("Kernel Memory limit not equal, expected : ["
                     + limit + "]" + ", got : ["
-                    + Metrics.systemMetrics().getKernelMemoryLimit() + "]");
+                    + kmemlimit + "]");
         }
         System.out.println("TEST PASSED!!!");
     }