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CONTIGMALLOC(9)	       FreeBSD Kernel Developer's Manual       CONTIGMALLOC(9)

NAME
     contigmalloc, contigfree -- manage	contiguous kernel physical memory

SYNOPSIS
     #include <sys/types.h>
     #include <sys/malloc.h>

     void *
     contigmalloc(unsigned long	size, struct malloc_type *type,	int flags,
	 vm_paddr_t low, vm_paddr_t high, unsigned long	alignment,
	 unsigned long boundary);

     void
     contigfree(void *addr, unsigned long size,	struct malloc_type *type);

DESCRIPTION
     The contigmalloc()	function allocates size	bytes of contiguous physical
     memory that is aligned to alignment bytes,	and which does not cross a
     boundary of boundary bytes.  If successful, the allocation	will reside
     between physical addresses	low and	high.  The returned pointer points to
     a wired kernel virtual address range of size bytes	allocated from the
     kernel virtual address (KVA) map.

     The flags parameter modifies contigmalloc()'s behaviour as	follows:

     M_ZERO  Causes the	allocated physical memory to be	zero filled.
     Other flags (if present) are ignored.

     The contigfree() function deallocates memory allocated by a previous call
     to	contigmalloc().

IMPLEMENTATION NOTES
     The contigmalloc()	function does not sleep	waiting	for memory resources
     to	be freed up, but instead scans available physical memory a small num-
     ber 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.

RETURN VALUES
     The contigmalloc()	function returns a kernel virtual address if alloca-
     tion succeeds, or NULL otherwise.

EXAMPLES
     void *p;
     p = contigmalloc(8192, M_DEVBUF, M_ZERO, 0, (1L <<	22),
	 32 * 1024, 1024 * 1024);

     Ask for 8192 bytes	of zero-filled memory residing between physical
     address 0 and 4194303 inclusive, aligned to a 32K boundary	and not	cross-
     ing a 1M address boundary.

SEE ALSO
     malloc(9)

DIAGNOSTICS
     The contigmalloc()	function will panic if size is zero, or	if alignment
     or	boundary is not	a power	of two.

FreeBSD	11.1			August 10, 2004			  FreeBSD 11.1
NAME | SYNOPSIS | DESCRIPTION | IMPLEMENTATION NOTES | RETURN VALUES | EXAMPLES | SEE ALSO | DIAGNOSTICS

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