issue-489: added unit test for chromium-style decommitting

src/tests/tcmalloc_unittest.cc

@@ -869,17 +869,17 @@ static size_t GetUnmappedBytes() {
 }
 #endif
 
-class AggressiveDecommitDisabler {
+class AggressiveDecommitChanger {
   size_t old_value_;
 public:
-  AggressiveDecommitDisabler() {
+  AggressiveDecommitChanger(size_t new_value) {
     MallocExtension *inst = MallocExtension::instance();
     bool rv = inst->GetNumericProperty("tcmalloc.aggressive_memory_decommit", &old_value_);
     CHECK_CONDITION(rv);
-    rv = inst->SetNumericProperty("tcmalloc.aggressive_memory_decommit", 0);
+    rv = inst->SetNumericProperty("tcmalloc.aggressive_memory_decommit", new_value);
     CHECK_CONDITION(rv);
   }
-  ~AggressiveDecommitDisabler() {
+  ~AggressiveDecommitChanger() {
     MallocExtension *inst = MallocExtension::instance();
     bool rv = inst->SetNumericProperty("tcmalloc.aggressive_memory_decommit", old_value_);
     CHECK_CONDITION(rv);
@@ -897,7 +897,7 @@ static void TestReleaseToSystem() {
   const double old_tcmalloc_release_rate = FLAGS_tcmalloc_release_rate;
   FLAGS_tcmalloc_release_rate = 0;
 
-  AggressiveDecommitDisabler disabler;
+  AggressiveDecommitChanger disabler(0);
 
   static const int MB = 1048576;
   void* a = malloc(MB);
@@ -949,6 +949,51 @@ static void TestReleaseToSystem() {
 #endif   // #ifndef DEBUGALLOCATION
 }
 
+static void TestAggressiveDecommit() {
+  // Debug allocation mode adds overhead to each allocation which
+  // messes up all the equality tests here.  I just disable the
+  // teset in this mode.
+#ifndef DEBUGALLOCATION
+
+  if(!HaveSystemRelease) return;
+
+  fprintf(LOGSTREAM, "Testing aggressive de-commit\n");
+
+  AggressiveDecommitChanger enabler(1);
+
+  static const int MB = 1048576;
+  void* a = malloc(MB);
+  void* b = malloc(MB);
+
+  size_t starting_bytes = GetUnmappedBytes();
+
+  // ReleaseToSystem shouldn't do anything either.
+  MallocExtension::instance()->ReleaseToSystem(MB);
+  EXPECT_EQ(starting_bytes, GetUnmappedBytes());
+
+  free(a);
+
+  // The span to release should be 1MB.
+  EXPECT_EQ(starting_bytes + MB, GetUnmappedBytes());
+
+  free(b);
+
+  EXPECT_EQ(starting_bytes + 2*MB, GetUnmappedBytes());
+
+  // Nothing else to release.
+  MallocExtension::instance()->ReleaseFreeMemory();
+  EXPECT_EQ(starting_bytes + 2*MB, GetUnmappedBytes());
+
+  a = malloc(MB);
+  free(a);
+
+  EXPECT_EQ(starting_bytes + 2*MB, GetUnmappedBytes());
+
+  fprintf(LOGSTREAM, "Done testing aggressive de-commit\n");
+
+#endif   // #ifndef DEBUGALLOCATION
+}
+
 // On MSVC10, in release mode, the optimizer convinces itself
 // g_no_memory is never changed (I guess it doesn't realize OnNoMemory
 // might be called).  Work around this by setting the var volatile.
@@ -1327,6 +1372,7 @@ static int RunAllTests(int argc, char** argv) {
   TestHugeThreadCache();
   TestRanges();
   TestReleaseToSystem();
+  TestAggressiveDecommit();
   TestSetNewMode();
 
   return 0;