home | help 
CONTIGMALLOC(9) 	    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 be-
     tween 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 number  of
     times for a suitably sized free address range before giving up.  Memory al-
     location  is  done  on a first-fit basis, starting from the top of the pro-
     vided address range.

RETURN VALUES
     The contigmalloc() function returns a kernel virtual address if  allocation
     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  crossing  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 5.3			 August 10, 2004		 CONTIGMALLOC(9)
home | help