162 lines
3.9 KiB
HTML
162 lines
3.9 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of MALLOC_TRIM</TITLE>
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</HEAD><BODY>
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<H1>MALLOC_TRIM</H1>
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Section: Linux Programmer's Manual (3)<BR>Updated: 2019-05-09<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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malloc_trim - release free memory from the heap
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/malloc.h">malloc.h</A>></B>
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<P>
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<B>int malloc_trim(size_t </B><I>pad</I><B>);</B>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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The
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<B>malloc_trim</B>()
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function attempts to release free memory from the heap
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(by calling
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<B><A HREF="/cgi-bin/man/man2html?2+sbrk">sbrk</A></B>(2)
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or
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<B><A HREF="/cgi-bin/man/man2html?2+madvise">madvise</A></B>(2)
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with suitable arguments).
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<P>
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The
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<I>pad</I>
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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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<B><A HREF="/cgi-bin/man/man2html?2+sbrk">sbrk</A></B>(2).
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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The
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<B>malloc_trim</B>()
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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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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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No errors are defined.
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<A NAME="lbAG"> </A>
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<H2>ATTRIBUTES</H2>
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For an explanation of the terms used in this section, see
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<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
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<TABLE BORDER>
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<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
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<TR VALIGN=top><TD>
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<B>malloc_trim</B>()
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</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
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</TABLE>
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<P>
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<A NAME="lbAH"> </A>
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<H2>CONFORMING TO</H2>
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This function is a GNU extension.
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<A NAME="lbAI"> </A>
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<H2>NOTES</H2>
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This function is automatically called by
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<B><A HREF="/cgi-bin/man/man2html?3+free">free</A></B>(3)
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in certain circumstances; see the discussion of
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<B>M_TOP_PAD</B>
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and
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<B>M_TRIM_THRESHOLD</B>
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in
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<B><A HREF="/cgi-bin/man/man2html?3+mallopt">mallopt</A></B>(3).
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<P>
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Only the main heap (using
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<B><A HREF="/cgi-bin/man/man2html?2+sbrk">sbrk</A></B>(2))
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honors the
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<I>pad</I>
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argument; thread heaps do not.
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<P>
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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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<P>
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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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<A NAME="lbAJ"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?2+sbrk">sbrk</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?3+malloc">malloc</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+mallopt">mallopt</A></B>(3)
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<A NAME="lbAK"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="1"><A HREF="#lbAB">NAME</A><DD>
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<DT id="2"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="3"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="4"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="5"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="6"><A HREF="#lbAG">ATTRIBUTES</A><DD>
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<DT id="7"><A HREF="#lbAH">CONFORMING TO</A><DD>
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<DT id="8"><A HREF="#lbAI">NOTES</A><DD>
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<DT id="9"><A HREF="#lbAJ">SEE ALSO</A><DD>
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<DT id="10"><A HREF="#lbAK">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:47 GMT, March 31, 2021
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