xref: /dflybsd-src/share/man/man9/contigmalloc.9 (revision 86d7f5d305c6adaa56ff4582ece9859d73106103)

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.\" $FreeBSD: src/share/man/man9/contigmalloc.9,v 1.5 2005/01/21 08:36:40 ru Exp $
.\" $DragonFly: src/share/man/man9/contigmalloc.9,v 1.1 2008/01/19 08:23:17 swildner Exp $
.\"
.Dd January 19, 2008
.Dt CONTIGMALLOC 9
.Os
.Sh NAME
.Nm contigmalloc ,
.Nm 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.
The
.Fa type
argument is ignored.
.Pp
The
.Fa flags
parameter modifies
.Fn contigmalloc Ns Ap s
behavior as follows:
.Bl -tag -width ".Dv M_WAITOK" -offset indent
.It Dv M_WAITOK
Causes
.Fn contigmalloc
to try flushing the active page queue in its second pass.
Note that (unlike
.Fn kmalloc M_WAITOK )
.Fn contigmalloc M_WAITOK
can still return NULL.
.It Dv M_ZERO
Causes the allocated physical memory to be zero filled.
.El
.Pp
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, starting from the
top of the provided address range.
.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 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 SEE ALSO
.Xr kmalloc 9