8216975: Using ForceNUMA does not disable adaptive sizing with parall…

…el gc

Reviewed-by: kbarrett, tschatzl, lkorinth

src/hotspot/os/linux/os_linux.cpp

@@ -5127,8 +5127,9 @@ void os::Linux::numa_init() {
   } else {
     if ((Linux::numa_max_node() < 1) || Linux::is_bound_to_single_node()) {
       // If there's only one node (they start from 0) or if the process
-      // is bound explicitly to a single node using membind, disable NUMA.
-      UseNUMA = false;
+      // is bound explicitly to a single node using membind, disable NUMA unless
+      // user explicilty forces NUMA optimizations on single-node/UMA systems
+      UseNUMA = ForceNUMA;
     } else {
 
       LogTarget(Info,os) log;
@@ -5167,10 +5168,6 @@ void os::Linux::numa_init() {
       UseAdaptiveNUMAChunkSizing = false;
     }
   }
-
-  if (!UseNUMA && ForceNUMA) {
-    UseNUMA = true;
-  }
 }
 
 // this is called _after_ the global arguments have been parsed

src/hotspot/os/solaris/os_solaris.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -3934,13 +3934,11 @@ jint os::init_2(void) {
       size_t lgrp_num = os::numa_get_leaf_groups(lgrp_ids, lgrp_limit);
       FREE_C_HEAP_ARRAY(int, lgrp_ids);
       if (lgrp_num < 2) {
-        // There's only one locality group, disable NUMA.
-        UseNUMA = false;
+        // There's only one locality group, disable NUMA unless
+        // user explicilty forces NUMA optimizations on single-node/UMA systems
+        UseNUMA = ForceNUMA;
       }
     }
-    if (!UseNUMA && ForceNUMA) {
-      UseNUMA = true;
-    }
   }
 
   Solaris::signal_sets_init();