xref: /freebsd/share/man/man9/contigmalloc.9 (revision 39beb93c3f8bdbf72a61fda42300b5ebed7390c8)
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26.\" $FreeBSD$
27.\"
28.Dd July 19, 2007
29.Dt CONTIGMALLOC 9
30.Os
31.Sh NAME
32.Nm contigmalloc , contigfree
33.Nd manage contiguous kernel physical memory
34.Sh SYNOPSIS
35.In sys/types.h
36.In sys/malloc.h
37.Ft "void *"
38.Fo contigmalloc
39.Fa "unsigned long size"
40.Fa "struct malloc_type *type"
41.Fa "int flags"
42.Fa "vm_paddr_t low"
43.Fa "vm_paddr_t high"
44.Fa "unsigned long alignment"
45.Fa "unsigned long boundary"
46.Fc
47.Ft void
48.Fo contigfree
49.Fa "void *addr"
50.Fa "unsigned long size"
51.Fa "struct malloc_type *type"
52.Fc
53.Sh DESCRIPTION
54The
55.Fn contigmalloc
56function allocates
57.Fa size
58bytes of contiguous physical memory that is aligned to
59.Fa alignment
60bytes, and which does not cross a boundary of
61.Fa boundary
62bytes.
63If successful, the allocation will reside between physical addresses
64.Fa low
65and
66.Fa high .
67The returned pointer points to a wired kernel virtual
68address range of
69.Fa size
70bytes allocated from the kernel virtual address (KVA) map.
71.Pp
72The
73.Fa flags
74parameter modifies
75.Fn contigmalloc Ns 's
76behaviour as follows:
77.Bl -tag -width indent
78.It Dv M_ZERO
79Causes the allocated physical memory to be zero filled.
80.It Dv M_NOWAIT
81Causes
82.Fn contigmalloc
83to return
84.Dv NULL
85if the request cannot be immediately fulfilled due to resource shortage.
86.El
87.Pp
88Other flags (if present) are ignored.
89.Pp
90The
91.Fn contigfree
92function deallocates memory allocated by a previous call to
93.Fn contigmalloc .
94.Sh IMPLEMENTATION NOTES
95The
96.Fn contigmalloc
97function does not sleep waiting for memory resources to be freed up,
98but instead actively reclaims pages before giving up.
99However, unless
100.Dv M_NOWAIT
101is specified, it may select a page for reclamation that must first be
102written to backing storage, causing it to sleep.
103.Sh RETURN VALUES
104The
105.Fn contigmalloc
106function returns a kernel virtual address if allocation succeeds,
107or
108.Dv NULL
109otherwise.
110.Sh EXAMPLES
111.Bd -literal
112void *p;
113p = contigmalloc(8192, M_DEVBUF, M_ZERO, 0, (1L << 22),
114    32 * 1024, 1024 * 1024);
115.Ed
116.Pp
117Ask for 8192 bytes of zero-filled memory residing between physical
118address 0 and 4194303 inclusive, aligned to a 32K boundary and not
119crossing a 1M address boundary.
120.Sh DIAGNOSTICS
121The
122.Fn contigmalloc
123function will panic if
124.Fa size
125is zero, or if
126.Fa alignment
127or
128.Fa boundary
129is not a power of two.
130.Sh SEE ALSO
131.Xr malloc 9 ,
132.Xr memguard 9
133