2 .\" Copyright (c) 1996 The NetBSD Foundation, Inc.
3 .\" All rights reserved.
5 .\" This code is derived from software contributed to The NetBSD Foundation
6 .\" by Paul Kranenburg.
8 .\" Redistribution and use in source and binary forms, with or without
9 .\" modification, are permitted provided that the following conditions
11 .\" 1. Redistributions of source code must retain the above copyright
12 .\" notice, this list of conditions and the following disclaimer.
13 .\" 2. Redistributions in binary form must reproduce the above copyright
14 .\" notice, this list of conditions and the following disclaimer in the
15 .\" documentation and/or other materials provided with the distribution.
16 .\" 3. All advertising materials mentioning features or use of this software
17 .\" must display the following acknowledgement:
18 .\" This product includes software developed by the NetBSD
19 .\" Foundation, Inc. and its contributors.
20 .\" 4. Neither the name of The NetBSD Foundation nor the names of its
21 .\" contributors may be used to endorse or promote products derived
22 .\" from this software without specific prior written permission.
24 .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
25 .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
26 .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
27 .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
28 .\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
29 .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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31 .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
32 .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
33 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
34 .\" POSSIBILITY OF SUCH DAMAGE.
36 .\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $
37 .\" $FreeBSD: src/share/man/man9/malloc.9,v 1.42 2005/02/22 17:20:20 brueffer Exp $
38 .\" $DragonFly: src/share/man/man9/kmalloc.9,v 1.8 2008/01/19 08:23:17 swildner Exp $
51 .Nd kernel memory management routines
56 .Fn kmalloc "unsigned long size" "struct malloc_type *type" "int flags"
57 .Fn MALLOC space cast "unsigned long size" "struct malloc_type *type" "int flags"
59 .Fn kfree "void *addr" "struct malloc_type *type"
60 .Fn FREE "void *addr" "struct malloc_type *type"
62 .Fn krealloc "void *addr" "unsigned long size" "struct malloc_type *type" "int flags"
63 .Fn MALLOC_DECLARE type
67 .Fn MALLOC_DEFINE type shortdesc longdesc
71 function allocates uninitialized memory in kernel address space for an
72 object whose size is specified by
77 function releases memory at address
79 that was previously allocated by
82 The memory is not zeroed.
83 The kernel implementation of
92 function changes the size of the previously allocated memory referenced by
97 The contents of the memory are unchanged up to the lesser of the new and
99 Note that the returned value may differ from
101 If the requested memory cannot be allocated,
103 is returned and the memory referenced by
105 is valid and unchanged.
112 function behaves identically to
114 for the specified size.
118 macro variant is functionally equivalent to
119 .Bd -literal -offset indent
120 (space) = (cast)kmalloc((u_long)(size), type, flags)
125 macro variant is equivalent to
126 .Bd -literal -offset indent
130 Unlike its standard C library counterpart
132 the kernel version takes two more arguments.
135 argument further qualifies
137 operational characteristics as follows:
138 .Bl -tag -width indent
140 Causes the allocated memory to be set to all zeros.
148 if the request cannot be immediately fulfilled due to resource shortage.
151 is required when running in an interrupt context.
153 Indicates that it is OK to wait for resources.
154 If the request cannot be immediately fulfilled, the current process is put
155 to sleep to wait for resources to be released by other processes.
160 functions cannot return
168 to dig into the system's reserved free pages looking for enough room to
169 perform the allocation.
170 This is typically used in interrupts where you cannot afford
174 Indicates that the system can dig into its reserve in order to obtain the
176 This option used to be called
178 but has been renamed to something more obvious.
179 This option has been deprecated and is slowly being removed from the kernel,
180 and so should not be used with any new code.
183 Exactly one of either
191 argument is used to perform statistics on memory usage, and for
193 It can be used to identify multiple allocations.
194 The statistics can be examined by
206 .Bd -literal -offset indent
207 /* sys/something/foo_extern.h */
209 MALLOC_DECLARE(M_FOOBUF);
211 /* sys/something/foo_main.c */
213 MALLOC_DEFINE(M_FOOBUF, "foobuffers", "Buffers to foo data into the ether");
215 /* sys/something/foo_subr.c */
218 MALLOC(buf, struct foo_buf *, sizeof *buf, M_FOOBUF, M_NOWAIT);
221 .Sh IMPLEMENTATION NOTES
222 The memory allocator allocates memory in chunks that have size a power
223 of two for requests up to the size of a page of memory.
224 For larger requests, one or more pages is allocated.
225 While it should not be relied upon, this information may be useful for
226 optimizing the efficiency of memory use.
232 functions return a kernel virtual address that is suitably aligned for
233 storage of any type of object, or
235 if the request could not be satisfied (implying that
239 A kernel compiled with the
241 configuration option attempts to detect memory corruption caused by
242 such things as writing outside the allocated area and imbalanced calls to the
247 Failing consistency checks will cause a panic or a system console