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

     contigmalloc, contigfree — manage contiguous kernel physical memory

     #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);

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

     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.

	     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().

     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.

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

     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.

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

     malloc(9), memguard(9)

BSD				 July 19, 2007				   BSD

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