freebsd-dev/share/man/man9/contigmalloc.9
Joseph Koshy c4e99bb025 A manual page for contigmalloc(9).
Reviewed by:	ru
2004-03-06 02:09:17 +00:00

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.Dd March 4, 2004
.Dt CONTIGMALLOC 9
.Os
.Sh NAME
.Nm contigmalloc , contigfree
.Nd manage contiguous kernel physical memory
.Sh SYNOPSIS
.In sys/types.h
.In sys/malloc.h
.Ft "void *"
.Fo contigmalloc
.Fa "unsigned long size"
.Fa "struct malloc_type *type"
.Fa "int flags"
.Fa "vm_paddr_t low"
.Fa "vm_paddr_t high"
.Fa "unsigned long alignment"
.Fa "unsigned long boundary"
.Fc
.Ft void
.Fo contigfree
.Fa "void *addr"
.Fa "unsigned long size"
.Fa "struct malloc_type *type"
.Fc
.Sh DESCRIPTION
The
.Fn contigmalloc
function allocates
.Fa size
bytes of contiguous physical memory that is aligned to
.Fa alignment
bytes, and which does not cross a boundary of
.Fa boundary
bytes.
If successful, the allocation will reside between physical addresses
.Fa low
and
.Fa high .
The returned pointer points to a wired kernel virtual
address range of
.Fa size
bytes allocated from the kernel virtual address (KVA) map.
.Pp
The
.Fa flags
parameter modifies
.Fn contigmalloc Ns 's
behaviour as follows:
.Bl -tag -width indent
.It Dv M_ZERO
Causes the allocated physical memory to be zero filled.
.El
Other flags (if present) are ignored.
.Pp
The
.Fn contigfree
function deallocates memory allocated by a previous call to
.Fn contigmalloc .
.Sh IMPLEMENTATION NOTES
The
.Fn contigmalloc
function does not sleep waiting for memory resources to be freed up,
but instead scans available physical memory a small number of times
for a suitably sized free address range before giving up.
Memory allocation is done on a first-fit basis.
.Sh RETURN VALUES
The
.Fn contigmalloc
function returns a kernel virtual address if allocation succeeds,
or
.Dv NULL
otherwise.
.Sh EXAMPLES
.Bd -literal
void *p;
p = contigmalloc(8192, M_DEVBUF, M_ZERO, 0, (1L << 22),
32 * 1024, 1024 * 1024);
.Ed
.Pp
Ask for 8192 bytes of zero-filled memory residing between physical
address 0 and 4194303 inclusive, aligned to a 32K boundary and not
crossing a 1M address boundary.
.Sh SEE ALSO
.Xr malloc 9
.Sh DIAGNOSTICS
The
.Fn contigmalloc
function will panic if
.Fa size
is zero, or if
.Fa alignment
or
.Fa boundary
is not a power of two.
.Sh BUGS
The
.Fa type
argument to
.Fn contigmalloc
and
.Fn contigfree
is ignored.