1// Copyright (c) 2005, Google Inc.
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3//
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7//
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17//
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29
30// ---
31// Author: Sanjay Ghemawat
32//
33// Routine that uses sbrk/mmap to allocate memory from the system.
34// Useful for implementing malloc.
35
36#ifndef TCMALLOC_SYSTEM_ALLOC_H_
37#define TCMALLOC_SYSTEM_ALLOC_H_
38
39#include <config.h>
40#include <stddef.h>                     // for size_t
41
42class SysAllocator;
43
44// REQUIRES: "alignment" is a power of two or "0" to indicate default alignment
45//
46// Allocate and return "N" bytes of zeroed memory.
47//
48// If actual_bytes is NULL then the returned memory is exactly the
49// requested size.  If actual bytes is non-NULL then the allocator
50// may optionally return more bytes than asked for (i.e. return an
51// entire "huge" page if a huge page allocator is in use).
52//
53// The returned pointer is a multiple of "alignment" if non-zero. The
54// returned pointer will always be aligned suitably for holding a
55// void*, double, or size_t. In addition, if this platform defines
56// CACHELINE_ALIGNED, the return pointer will always be cacheline
57// aligned.
58//
59// Returns NULL when out of memory.
60extern void* TCMalloc_SystemAlloc(size_t bytes, size_t *actual_bytes,
61                                  size_t alignment = 0);
62
63// This call is a hint to the operating system that the pages
64// contained in the specified range of memory will not be used for a
65// while, and can be released for use by other processes or the OS.
66// Pages which are released in this way may be destroyed (zeroed) by
67// the OS.  The benefit of this function is that it frees memory for
68// use by the system, the cost is that the pages are faulted back into
69// the address space next time they are touched, which can impact
70// performance.  (Only pages fully covered by the memory region will
71// be released, partial pages will not.)
72extern void TCMalloc_SystemRelease(void* start, size_t length);
73
74// Called to ressurect memory which has been previously released
75// to the system via TCMalloc_SystemRelease.  An attempt to
76// commit a page that is already committed does not cause this
77// function to fail.
78extern void TCMalloc_SystemCommit(void* start, size_t length);
79
80// Guards the first page in the supplied range of memory and returns the size
81// of the guard page. Will return 0 if a guard cannot be added to the page
82// (e.g. start is not aligned or size is not large enough).
83extern size_t TCMalloc_SystemAddGuard(void* start, size_t size);
84
85// The current system allocator.
86extern PERFTOOLS_DLL_DECL SysAllocator* sys_alloc;
87
88#endif /* TCMALLOC_SYSTEM_ALLOC_H_ */
89