[thirdparty/man-pages.git] / man3 / malloc_trim.3

'\" t
.\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
.TH MALLOC_TRIM 3  2015-07-23 "Linux" "Linux Programmer's Manual"
.SH NAME
malloc_trim \- release free memory from the top of the heap
.SH SYNOPSIS
.B #include <malloc.h>

.BI "int malloc_trim(size_t "  pad );
.SH DESCRIPTION
The
.BR malloc_trim ()
function attempts to release free memory at the top of the heap
(by calling
.BR sbrk (2)
with a suitable argument).

The
.I pad
argument specifies the amount of free space to leave untrimmed
at the top of the heap.
If this argument is 0, only the minimum amount of memory is maintained
at the top of the heap (i.e., one page or less).
A nonzero argument can be used to maintain some trailing space
at the top of the heap in order to allow future allocations
to be made without having to extend the heap with
.BR sbrk (2).
.SH RETURN VALUE
The
.BR malloc_trim ()
function returns 1 if memory was actually released back to the system,
or 0 if it was not possible to release any memory.
.SH ERRORS
No errors are defined.
.\" .SH VERSIONS
.\" Available already in glibc 2.0, possibly earlier
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lb
l l l.
Interface	Attribute	Value
T{
.BR malloc_trim ()
T}	Thread safety	MT-Safe
.TE

.SH CONFORMING TO
This function is a GNU extension.
.SH NOTES
This function is automatically called by
.BR free (3)
in certain circumstances; see the discussion of
.B M_TOP_PAD
and
.B M_TRIM_THRESHOLD
in
.BR mallopt (3).

This function cannot release free memory located at places
other than the top of the heap.

This function releases only memory in the main arena.
.\" malloc/malloc.c::mTRIm():
.\"     return result | (av == &main_arena ? sYSTRIm (pad, av) : 0);
.SH SEE ALSO
.BR sbrk (2),
.BR malloc (3),
.BR mallopt (3)
Commit	Line	Data
a15b0e60 MK	1	'\" t
	2	.\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com>
	3	.\"
93015253	4	.\" %%%LICENSE_START(VERBATIM)
a15b0e60 MK	5	.\" Permission is granted to make and distribute verbatim copies of this
	6	.\" manual provided the copyright notice and this permission notice are
	7	.\" preserved on all copies.
	8	.\"
	9	.\" Permission is granted to copy and distribute modified versions of this
	10	.\" manual under the conditions for verbatim copying, provided that the
	11	.\" entire resulting derived work is distributed under the terms of a
	12	.\" permission notice identical to this one.
	13	.\"
	14	.\" Since the Linux kernel and libraries are constantly changing, this
	15	.\" manual page may be incorrect or out-of-date. The author(s) assume no
	16	.\" responsibility for errors or omissions, or for damages resulting from
	17	.\" the use of the information contained herein. The author(s) may not
	18	.\" have taken the same level of care in the production of this manual,
	19	.\" which is licensed free of charge, as they might when working
	20	.\" professionally.
	21	.\"
	22	.\" Formatted or processed versions of this manual, if unaccompanied by
	23	.\" the source, must acknowledge the copyright and authors of this work.
4b72fb64	24	.\" %%%LICENSE_END
a15b0e60	25	.\"
5722c835	26	.TH MALLOC_TRIM 3 2015-07-23 "Linux" "Linux Programmer's Manual"
a15b0e60 MK	27	.SH NAME
	28	malloc_trim \- release free memory from the top of the heap
	29	.SH SYNOPSIS
	30	.B #include <malloc.h>
	31
7b7fbe78	32	.BI "int malloc_trim(size_t " pad );
a15b0e60 MK	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
0cc0b5e4 ZL	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
a15b0e60 MK	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.
73354f23	87
ec18b513	88	This function releases only memory in the main arena.
a15b0e60 MK	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)