man3/malloc_trim.3

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  26 .TH MALLOC_TRIM 3  2015-07-23 "Linux" "Linux Programmer's Manual"
  27 .SH NAME
  28 malloc_trim \- release free memory from the top of the heap
  29 .SH SYNOPSIS
  30 .B #include <malloc.h>
  31
  32 .BI "int malloc_trim(size_t "  pad );
  33 .SH DESCRIPTION
  34 The
  35 .BR malloc_trim ()
  36 function attempts to release free memory at the top of the heap
  37 (by calling
  38 .BR sbrk (2)
  39 with a suitable argument).
  40
  41 The
  42 .I pad
  43 argument specifies the amount of free space to leave untrimmed
  44 at the top of the heap.
  45 If this argument is 0, only the minimum amount of memory is maintained
  46 at the top of the heap (i.e., one page or less).
  47 A nonzero argument can be used to maintain some trailing space
  48 at the top of the heap in order to allow future allocations
  49 to be made without having to extend the heap with
  50 .BR sbrk (2).
  51 .SH RETURN VALUE
  52 The
  53 .BR malloc_trim ()
  54 function returns 1 if memory was actually released back to the system,
  55 or 0 if it was not possible to release any memory.
  56 .SH ERRORS
  57 No errors are defined.
  58 .\" .SH VERSIONS
  59 .\" Available already in glibc 2.0, possibly earlier
  60 .SH ATTRIBUTES
  61 For an explanation of the terms used in this section, see
  62 .BR attributes (7).
  63 .TS
  64 allbox;
  65 lb lb lb
  66 l l l.
  67 Interface       Attribute       Value
  68 T{
  69 .BR malloc_trim ()
  70 T}      Thread safety   MT-Safe
  71 .TE
  72
  73 .SH CONFORMING TO
  74 This function is a GNU extension.
  75 .SH NOTES
  76 This function is automatically called by
  77 .BR free (3)
  78 in certain circumstances; see the discussion of
  79 .B M_TOP_PAD
  80 and
  81 .B M_TRIM_THRESHOLD
  82 in
  83 .BR mallopt (3).
  84
  85 This function cannot release free memory located at places
  86 other than the top of the heap.
  87
  88 This function releases only memory in the main arena.
  89 .\" malloc/malloc.c::mTRIm():
  90 .\"     return result | (av == &main_arena ? sYSTRIm (pad, av) : 0);
  91 .SH SEE ALSO
  92 .BR sbrk (2),
  93 .BR malloc (3),
  94 .BR mallopt (3)