mirror of https://github.com/mkerrisk/man-pages
105 lines
3.1 KiB
Groff
105 lines
3.1 KiB
Groff
'\" t
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.\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.TH MALLOC_TRIM 3 2019-05-09 "Linux" "Linux Programmer's Manual"
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.SH NAME
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malloc_trim \- release free memory from the heap
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.SH SYNOPSIS
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.B #include <malloc.h>
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.PP
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.BI "int malloc_trim(size_t " pad );
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.SH DESCRIPTION
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The
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.BR malloc_trim ()
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function attempts to release free memory from the heap
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(by calling
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.BR sbrk (2)
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or
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.BR madvise (2)
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with suitable arguments).
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.PP
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The
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.I pad
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argument specifies the amount of free space to leave untrimmed
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at the top of the heap.
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If this argument is 0, only the minimum amount of memory is maintained
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at the top of the heap (i.e., one page or less).
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A nonzero argument can be used to maintain some trailing space
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at the top of the heap in order to allow future allocations
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to be made without having to extend the heap with
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.BR sbrk (2).
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.SH RETURN VALUE
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The
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.BR malloc_trim ()
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function returns 1 if memory was actually released back to the system,
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or 0 if it was not possible to release any memory.
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.SH ERRORS
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No errors are defined.
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.\" .SH VERSIONS
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.\" Available already in glibc 2.0, possibly earlier
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lb lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR malloc_trim ()
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T} Thread safety MT-Safe
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.TE
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.sp 1
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.SH CONFORMING TO
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This function is a GNU extension.
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.SH NOTES
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This function is automatically called by
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.BR free (3)
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in certain circumstances; see the discussion of
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.B M_TOP_PAD
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and
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.B M_TRIM_THRESHOLD
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in
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.BR mallopt (3).
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.PP
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Only the main heap (using
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.BR sbrk (2))
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honors the
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.I pad
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argument; thread heaps do not.
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.PP
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Since glibc 2.8 this function frees memory in all arenas and in all
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chunks with whole free pages.
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.\" See commit 68631c8eb92ff38d9da1ae34f6aa048539b199cc
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.\" (dated 2007-12-16) which adds iteration over all
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.\" arenas and frees all pages in chunks which are free.
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.PP
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Before glibc 2.8 this function only freed memory at the
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top of the heap in the main arena.
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.SH SEE ALSO
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.BR sbrk (2),
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.BR malloc (3),
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.BR mallopt (3)
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