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, vm_paddr_t boundary);
void
contigfree(void *addr,
unsigned long size, struct malloc_type
*type);
#include
<sys/param.h>
#include <sys/domainset.h>
void *
contigmalloc_domainset(unsigned long
size, struct malloc_type *type,
struct domainset *ds, int flags,
vm_paddr_t low, vm_paddr_t high,
unsigned long alignment, vm_paddr_t
boundary);
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
contigmalloc_domainset()
variant allows the caller to additionally specify a
numa(4) domain selection policy. See
domainset(9) for some example policies.
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 returnNULLif 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() or
contigmalloc_domainset().
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.
The contigfree() function does not accept
NULL as an address input, unlike
free(9).
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.