Major changes to the Chrome allocator....

third_party/tcmalloc/system-alloc.h

+// Copyright (c) 2005, Google Inc.
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+// 
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// ---
+// Author: Sanjay Ghemawat
+//
+// Routine that uses sbrk/mmap to allocate memory from the system.
+// Useful for implementing malloc.
+
+#ifndef TCMALLOC_SYSTEM_ALLOC_H_
+#define TCMALLOC_SYSTEM_ALLOC_H_
+
+#include <config.h>
+#include "internal_logging.h"
+
+// REQUIRES: "alignment" is a power of two or "0" to indicate default alignment
+//
+// Allocate and return "N" bytes of zeroed memory.
+//
+// If actual_bytes is NULL then the returned memory is exactly the
+// requested size.  If actual bytes is non-NULL then the allocator
+// may optionally return more bytes than asked for (i.e. return an
+// entire "huge" page if a huge page allocator is in use).
+//
+// The returned pointer is a multiple of "alignment" if non-zero.
+//
+// Returns NULL when out of memory.
+extern void* TCMalloc_SystemAlloc(size_t bytes, size_t *actual_bytes,
+                                  size_t alignment = 0);
+
+// This call is a hint to the operating system that the pages
+// contained in the specified range of memory will not be used for a
+// while, and can be released for use by other processes or the OS.
+// Pages which are released in this way may be destroyed (zeroed) by
+// the OS.  The benefit of this function is that it frees memory for
+// use by the system, the cost is that the pages are faulted back into
+// the address space next time they are touched, which can impact
+// performance.  (Only pages fully covered by the memory region will
+// be released, partial pages will not.)
+extern void TCMalloc_SystemRelease(void* start, size_t length);
+
+// Called to ressurect memory which has been previously released
+// to the system via TCMalloc_SystemRelease.  An attempt to
+// commit a page that is already committed does not cause this
+// function to fail.
+extern void TCMalloc_SystemCommit(void* start, size_t length);
+
+// Interface to a pluggable system allocator.
+class SysAllocator {
+ public:
+  SysAllocator() 
+    : usable_(true), 
+      failed_(false) {
+  };
+  virtual ~SysAllocator() {};
+
+  virtual void* Alloc(size_t size, size_t *actual_size, size_t alignment) = 0;
+
+  // Populate the map with whatever properties the specified allocator finds
+  // useful for debugging (such as number of bytes allocated and whether the
+  // allocator has failed).  The callee is responsible for any necessary
+  // locking (and avoiding deadlock).
+  virtual void DumpStats(TCMalloc_Printer* printer) = 0;
+
+  // So the allocator can be turned off at compile time
+  bool usable_;
+
+  // Did this allocator fail? If so, we don't need to retry more than twice.
+  bool failed_;
+};
+
+// Register a new system allocator. The priority determines the order in
+// which the allocators will be invoked. Allocators with numerically lower
+// priority are tried first. To keep things simple, the priority of various
+// allocators is known at compile time.
+//
+// Valid range of priorities: [0, kMaxDynamicAllocators)
+//
+// Please note that we can't use complex data structures and cause
+// recursive calls to malloc within this function. So all data structures
+// are statically allocated.
+//
+// Returns true on success. Does nothing on failure.
+extern PERFTOOLS_DLL_DECL bool RegisterSystemAllocator(SysAllocator *allocator,
+                                                       int priority);
+
+// Number of SysAllocators known to call RegisterSystemAllocator
+static const int kMaxDynamicAllocators = 2;
+
+// Retrieve the current state of various system allocators.
+extern PERFTOOLS_DLL_DECL void DumpSystemAllocatorStats(TCMalloc_Printer* printer);
+
+#endif /* TCMALLOC_SYSTEM_ALLOC_H_ */