--- a/src/hotspot/share/services/virtualMemoryTracker.cpp	Tue Jan 30 10:38:17 2018 +0100
+++ b/src/hotspot/share/services/virtualMemoryTracker.cpp	Tue Jan 30 16:26:40 2018 +0100
@@ -65,26 +65,16 @@
     }
 
     if (rgn->adjacent_to(addr, size)) {
-      if (rgn->call_stack()->equals(stack)) {
+      // special case to expand prior region if there is no next region
+      LinkedListNode<CommittedMemoryRegion>* next = node->next();
+      if (next == NULL && rgn->call_stack()->equals(stack)) {
+        VirtualMemorySummary::record_uncommitted_memory(rgn->size(), flag());
         // the two adjacent regions have the same call stack, merge them
         rgn->expand_region(addr, size);
-        VirtualMemorySummary::record_committed_memory(size, flag());
-
-        // maybe merge with the next region
-        LinkedListNode<CommittedMemoryRegion>* next_node = node->next();
-        if (next_node != NULL) {
-          CommittedMemoryRegion* next = next_node->data();
-          if (next->call_stack()->equals(stack) && rgn->adjacent_to(next->base(), next->size())) {
-            // the two adjacent regions have the same call stack, merge them
-            rgn->expand_region(next->base(), next->size());
-
-            // the merge next_node needs to be removed from the list
-            _committed_regions.remove(next_node);
-          }
-        }
+        VirtualMemorySummary::record_committed_memory(rgn->size(), flag());
         return true;
       }
-    }
+      }
 
     if (rgn->overlap_region(addr, size)) {
       // Clear a space for this region in the case it overlaps with any regions.
@@ -97,10 +87,10 @@
     node = node->next();
   }
 
-  // New committed region
-  VirtualMemorySummary::record_committed_memory(size, flag());
-  return add_committed_region(committed_rgn);
-}
+    // New committed region
+    VirtualMemorySummary::record_committed_memory(size, flag());
+    return add_committed_region(committed_rgn);
+  }
 
 void ReservedMemoryRegion::set_all_committed(bool b) {
   if (all_committed() != b) {

--- a/test/hotspot/jtreg/runtime/NMT/VirtualAllocCommitMerge.java	Tue Jan 30 10:38:17 2018 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,283 +0,0 @@
-/*
- * Copyright (c) 2014, 2016, 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
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- */
-
-/*
- * @test
- * @summary Test merging of committed virtual memory and that we track it correctly
- * @key nmt jcmd
- * @library /test/lib
- * @modules java.base/jdk.internal.misc
- *          java.management
- * @build sun.hotspot.WhiteBox
- * @run main ClassFileInstaller sun.hotspot.WhiteBox
- * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -XX:NativeMemoryTracking=detail VirtualAllocCommitMerge
- *
- */
-
-import jdk.test.lib.process.ProcessTools;
-import jdk.test.lib.process.OutputAnalyzer;
-import jdk.test.lib.JDKToolFinder;
-
-import sun.hotspot.WhiteBox;
-
-public class VirtualAllocCommitMerge {
-
-    public static WhiteBox wb = WhiteBox.getWhiteBox();
-
-    public static void main(String args[]) throws Exception {
-        OutputAnalyzer output;
-        long commitSize = 128 * 1024; // 128KB
-        long reserveSize = 4 * 1024 * 1024; // 4096KB
-        long addr;
-
-        String pid = Long.toString(ProcessTools.getProcessId());
-        ProcessBuilder pb = new ProcessBuilder();
-
-        // reserve
-        addr = wb.NMTReserveMemory(reserveSize);
-        pb.command(new String[] { JDKToolFinder.getJDKTool("jcmd"), pid,
-                "VM.native_memory", "detail" });
-
-        output = new OutputAnalyzer(pb.start());
-        checkReservedCommittedSummary(output, "4096KB", "0KB");
-        checkReserved(output, addr, reserveSize, "4096KB");
-
-        long addrA = addr + (0 * commitSize);
-        long addrB = addr + (1 * commitSize);
-        long addrC = addr + (2 * commitSize);
-        long addrD = addr + (3 * commitSize);
-        long addrE = addr + (4 * commitSize);
-
-        // Test discontigous areas
-        {
-            // commit ACE
-            wb.NMTCommitMemory(addrA, commitSize);
-            wb.NMTCommitMemory(addrC, commitSize);
-            wb.NMTCommitMemory(addrE, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "384KB");
-            checkReserved(output, addr, reserveSize, "4096KB");
-
-            checkCommitted(output, addrA, commitSize, "128KB");
-            checkCommitted(output, addrC, commitSize, "128KB");
-            checkCommitted(output, addrE, commitSize, "128KB");
-
-            // uncommit ACE
-            wb.NMTUncommitMemory(addrA, commitSize);
-            wb.NMTUncommitMemory(addrC, commitSize);
-            wb.NMTUncommitMemory(addrE, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "0KB");
-        }
-
-        // Test contiguous areas
-        {
-            // commit AB
-            wb.NMTCommitMemory(addrA, commitSize);
-            wb.NMTCommitMemory(addrB, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "256KB");
-            checkReserved(output, addr, reserveSize, "4096KB");
-
-            checkCommitted(output, addrA, 2 * commitSize, "256KB");
-
-            // uncommit AB
-            wb.NMTUncommitMemory(addrA, commitSize);
-            wb.NMTUncommitMemory(addrB, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "0KB");
-        }
-
-        {
-            // commit BA
-            wb.NMTCommitMemory(addrB, commitSize);
-            wb.NMTCommitMemory(addrA, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "256KB");
-            checkReserved(output, addr, reserveSize, "4096KB");
-
-            checkCommitted(output, addrA, 2 * commitSize, "256KB");
-
-            // uncommit AB
-            wb.NMTUncommitMemory(addrB, commitSize);
-            wb.NMTUncommitMemory(addrA, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "0KB");
-        }
-
-        {
-            // commit ABC
-            wb.NMTCommitMemory(addrA, commitSize);
-            wb.NMTCommitMemory(addrB, commitSize);
-            wb.NMTCommitMemory(addrC, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "384KB");
-            checkReserved(output, addr, reserveSize, "4096KB");
-
-            checkCommitted(output, addrA, 3 * commitSize, "384KB");
-
-            // uncommit
-            wb.NMTUncommitMemory(addrA, commitSize);
-            wb.NMTUncommitMemory(addrB, commitSize);
-            wb.NMTUncommitMemory(addrC, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "0KB");
-        }
-
-        {
-            // commit ACB
-            wb.NMTCommitMemory(addrA, commitSize);
-            wb.NMTCommitMemory(addrC, commitSize);
-            wb.NMTCommitMemory(addrB, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "384KB");
-            checkReserved(output, addr, reserveSize, "4096KB");
-
-            checkCommitted(output, addrA, 3 * commitSize, "384KB");
-
-            // uncommit
-            wb.NMTUncommitMemory(addrA, commitSize);
-            wb.NMTUncommitMemory(addrC, commitSize);
-            wb.NMTUncommitMemory(addrB, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "0KB");
-        }
-
-        {
-            // commit BAC
-            wb.NMTCommitMemory(addrB, commitSize);
-            wb.NMTCommitMemory(addrA, commitSize);
-            wb.NMTCommitMemory(addrC, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "384KB");
-            checkReserved(output, addr, reserveSize, "4096KB");
-
-            checkCommitted(output, addrA, 3 * commitSize, "384KB");
-
-            // uncommit
-            wb.NMTUncommitMemory(addrB, commitSize);
-            wb.NMTUncommitMemory(addrA, commitSize);
-            wb.NMTUncommitMemory(addrC, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "0KB");
-        }
-
-        {
-            // commit BCA
-            wb.NMTCommitMemory(addrB, commitSize);
-            wb.NMTCommitMemory(addrC, commitSize);
-            wb.NMTCommitMemory(addrA, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "384KB");
-            checkReserved(output, addr, reserveSize, "4096KB");
-
-            checkCommitted(output, addrA, 3 * commitSize, "384KB");
-
-            // uncommit
-            wb.NMTUncommitMemory(addrB, commitSize);
-            wb.NMTUncommitMemory(addrC, commitSize);
-            wb.NMTUncommitMemory(addrA, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "0KB");
-        }
-
-        {
-            // commit CAB
-            wb.NMTCommitMemory(addrC, commitSize);
-            wb.NMTCommitMemory(addrA, commitSize);
-            wb.NMTCommitMemory(addrB, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "384KB");
-            checkReserved(output, addr, reserveSize, "4096KB");
-
-            checkCommitted(output, addrA, 3 * commitSize, "384KB");
-
-            // uncommit
-            wb.NMTUncommitMemory(addrC, commitSize);
-            wb.NMTUncommitMemory(addrA, commitSize);
-            wb.NMTUncommitMemory(addrB, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "0KB");
-        }
-
-        {
-            // commit CBA
-            wb.NMTCommitMemory(addrC, commitSize);
-            wb.NMTCommitMemory(addrB, commitSize);
-            wb.NMTCommitMemory(addrA, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "384KB");
-            checkReserved(output, addr, reserveSize, "4096KB");
-
-            checkCommitted(output, addrA, 3 * commitSize, "384KB");
-
-            // uncommit
-            wb.NMTUncommitMemory(addrC, commitSize);
-            wb.NMTUncommitMemory(addrB, commitSize);
-            wb.NMTUncommitMemory(addrA, commitSize);
-
-            output = new OutputAnalyzer(pb.start());
-            checkReservedCommittedSummary(output, "4096KB", "0KB");
-        }
-
-        // release
-        wb.NMTReleaseMemory(addr, reserveSize);
-        output = new OutputAnalyzer(pb.start());
-        output.shouldNotContain("Test (reserved=");
-        output.shouldNotMatch("\\[0x[0]*" + Long.toHexString(addr) + " - 0x[0]*"
-                + Long.toHexString(addr + reserveSize) + "\\] reserved 4096KB for Test");
-    }
-
-    public static void checkReservedCommittedSummary(OutputAnalyzer output, String reservedString, String committedString) {
-        output.shouldContain("Test (reserved=" + reservedString + ", committed=" + committedString + ")");
-    }
-
-    public static void checkReserved(OutputAnalyzer output, long addr, long size, String sizeString) {
-        output.shouldMatch("\\[0x[0]*" + Long.toHexString(addr) + " - 0x[0]*"
-                           + Long.toHexString(addr + size)
-                           + "\\] reserved 4096KB for Test");
-    }
-
-    public static void checkCommitted(OutputAnalyzer output, long addr, long size, String sizeString) {
-        output.shouldMatch("\\[0x[0]*" + Long.toHexString(addr) + " - 0x[0]*"
-                           + Long.toHexString(addr + size)
-                           + "\\] committed " + sizeString + " from.*");
-    }
-}