[NOT TO COMMIT!] Merge Chromium-specific changes in tcmalloc thru. the original gperftools r136.

third_party/tcmalloc/chromium/src/page_heap.h

Index: third_party/tcmalloc/chromium/src/page_heap.h
diff --git a/third_party/tcmalloc/chromium/src/page_heap.h b/third_party/tcmalloc/chromium/src/page_heap.h
index 19c143104fff4739adcdd52bd9e962e5021014e7..738c011214e32b5fe814b85590f12d30039815f7 100644
--- a/third_party/tcmalloc/chromium/src/page_heap.h
+++ b/third_party/tcmalloc/chromium/src/page_heap.h
@@ -75,6 +75,8 @@ namespace tcmalloc {
 // -------------------------------------------------------------------------
 
 // We use PageMap2<> for 32-bit and PageMap3<> for 64-bit machines.
+// ...except...
+// On Windows, we use TCMalloc_PageMap1_LazyCommit<> for 32-bit machines.
 // We also use a simple one-level cache for hot PageID-to-sizeclass mappings,
 // because sometimes the sizeclass is all the information we need.
 
@@ -88,7 +90,13 @@ template <int BITS> class MapSelector {
 // A two-level map for 32-bit machines
 template <> class MapSelector<32> {
  public:
+#ifdef WIN32
+// A flat map for 32-bit machines (with lazy commit of memory).
+  typedef TCMalloc_PageMap1_LazyCommit<32-kPageShift> Type;
+#else
+  // A two-level map for 32-bit machines
   typedef TCMalloc_PageMap2<32-kPageShift> Type;
+#endif
   typedef PackedCache<32-kPageShift, uint16_t> CacheType;
 };
 
@@ -146,6 +154,8 @@ class PERFTOOLS_DLL_DECL PageHeap {
     uint64_t system_bytes;    // Total bytes allocated from system
     uint64_t free_bytes;      // Total bytes on normal freelists
     uint64_t unmapped_bytes;  // Total bytes on returned freelists
+    uint64_t committed_bytes;  // Bytes committed, always <= system_bytes_.
+
   };
   inline Stats stats() const { return stats_; }
 
@@ -206,11 +216,13 @@ class PERFTOOLS_DLL_DECL PageHeap {
   // Never delay scavenging for more than the following number of
   // deallocated pages.  With 4K pages, this comes to 4GB of
   // deallocation.
-  static const int kMaxReleaseDelay = 1 << 20;
+  // Chrome:  Changed to 64MB
+  static const int kMaxReleaseDelay = 1 << 14;
 
   // If there is nothing to release, wait for so many pages before
   // scavenging again.  With 4K pages, this comes to 1GB of memory.
-  static const int kDefaultReleaseDelay = 1 << 18;
+  // Chrome:  Changed to 16MB
+  static const int kDefaultReleaseDelay = 1 << 12;
 
   // Pick the appropriate map and cache types based on pointer size
   typedef MapSelector<kAddressBits>::Type PageMap;
@@ -234,7 +246,6 @@ class PERFTOOLS_DLL_DECL PageHeap {
 
   // Statistics on system, free, and unmapped bytes
   Stats stats_;
-
   Span* SearchFreeAndLargeLists(Length n);
 
   bool GrowHeap(Length n);
@@ -263,6 +274,12 @@ class PERFTOOLS_DLL_DECL PageHeap {
   // appropriate free list, and adjust stats.
   void MergeIntoFreeList(Span* span);
 
+  // Commit the span.
+  void CommitSpan(Span* span);
+
+  // Decommit the span.
+  void DecommitSpan(Span* span);
+
   // Prepends span to appropriate free list, and adjusts stats.
   void PrependToFreeList(Span* span);