--- old/src/share/vm/logging/logStream.hpp	2017-06-18 08:42:39.220358000 +0200
+++ new/src/share/vm/logging/logStream.hpp	2017-06-18 08:42:38.344294200 +0200
@@ -32,9 +32,31 @@
 
 
 class LogStream : public outputStream {
-  bufferedStream  _current_line;
+
+  // Helper class, maintains the line buffer. For small line lengths,
+  // we avoid malloc and use a fixed sized member char array. If LogStream
+  // is allocated on the stack, this means small lines are assembled
+  // directly on the stack.
+  class LineBuffer {
+    char _smallbuf[128];
+    char* _buf;
+    size_t _cap;
+    size_t _pos;
+    void ensure_cap(size_t cap);
+  public:
+    LineBuffer();
+    ~LineBuffer();
+    const char* ptr() const { return _buf; }
+    void append(const char* s, size_t len);
+    void reset();
+  }; 
+  LineBuffer  _current_line;
   LogTargetHandle _log_handle;
 
+  // Prevent operator new for LogStream.
+//  static void* operator new (size_t);
+//   static void* operator new[] (size_t);
+  
 public:
   // Constructor to support creation from a LogTarget instance.
   //
@@ -65,10 +87,6 @@
   // LogStreamBase(level, tageset);
   LogStream(LogLevelType level, LogTagSet* tagset) : _log_handle(level, tagset) {}
 
-  ~LogStream() {
-    guarantee(_current_line.size() == 0, "Buffer not flushed. Missing call to print_cr()?");
-  }
-
 public:
   void write(const char* s, size_t len);
 };