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 reclamation that must first be written to backing storage, causing it to sleep.

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.

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)

Debian                                            July 19, 2007                                  CONTIGMALLOC(9)