|CONTIGMALLOC(9)||Kernel Developer's Manual||CONTIGMALLOC(9)|
contigfree — manage
contiguous kernel physical memory
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);
unsigned long size, struct malloc_type
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
The flags parameter
behaviour as follows:
- Causes the allocated physical memory to be zero filled.
contigmalloc() to return
NULLif the request cannot be immediately fulfilled due to resource shortage.
Other flags (if present) are ignored.
function deallocates memory allocated by a previous call to
contigmalloc() function does not sleep
waiting for memory resources to be freed up, but instead actively reclaims
pages before giving up. However, unless
specified, it may select a page for reclamation that must first be written
to backing storage, causing it to sleep.
contigfree() function does not accept
NULL as an address input, unlike
contigmalloc() function returns a
kernel virtual address if allocation succeeds, or
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.
contigmalloc() function will panic if
size is zero, or if alignment or
boundary is not a power of two.
|January 29, 2015||Debian|