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CONTIGMALLOC(9)		 BSD 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.

     M_NOWAIT
	     Causes contigmalloc() to return NULL if the request cannot be
	     immediately fulfilled due to resource shortage.

     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 actively reclaims pages before giving up.
     However, unless M_NOWAIT is specified, it may select a page for reclama‐
     tion that must first be written to backing storage, causing it to sleep.

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.

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

SEE ALSO
     malloc(9), memguard(9)

BSD				 July 19, 2007				   BSD
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