1// Copyright (c) 2005, 2007, Google Inc.
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3//
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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// REQUIRES: "alignment" is a power of two or "0" to indicate default alignment
40//
41// Allocate and return "N" bytes of zeroed memory.
42//
43// If actual_bytes is NULL then the returned memory is exactly the
44// requested size.  If actual bytes is non-NULL then the allocator
45// may optionally return more bytes than asked for (i.e. return an
46// entire "huge" page if a huge page allocator is in use).
47//
48// The returned pointer is a multiple of "alignment" if non-zero.
49//
50// Returns NULL when out of memory.
51extern void* TCMalloc_SystemAlloc(size_t bytes, size_t *actual_bytes,
52                                  size_t alignment = 0);
53
54// This call is a hint to the operating system that the pages
55// contained in the specified range of memory will not be used for a
56// while, and can be released for use by other processes or the OS.
57// Pages which are released in this way may be destroyed (zeroed) by
58// the OS.  The benefit of this function is that it frees memory for
59// use by the system, the cost is that the pages are faulted back into
60// the address space next time they are touched, which can impact
61// performance.  (Only pages fully covered by the memory region will
62// be released, partial pages will not.)
63extern void TCMalloc_SystemRelease(void* start, size_t length);
64
65extern void TCMalloc_SystemCommit(void* start, size_t length);
66
67#if !HAVE(MADV_FREE_REUSE) && !HAVE(MADV_DONTNEED) && !HAVE(MMAP) && !HAVE(VIRTUALALLOC)
68inline void TCMalloc_SystemRelease(void*, size_t) { }
69#endif
70
71#if !HAVE(VIRTUALALLOC) && !HAVE(MADV_FREE_REUSE)
72inline void TCMalloc_SystemCommit(void*, size_t) { }
73#endif
74
75#endif /* TCMALLOC_SYSTEM_ALLOC_H__ */
76