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
Thecontigmalloc()
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
type argument is ignored.
The flags parameter
modifies
contigmalloc()'s
behavior as follows:
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 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 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.