|CONTIGMALLOC(9)||Kernel Developer's Manual||CONTIGMALLOC(9)|
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
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:
- 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.
contigfree() 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
M_NOWAITis 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.
SEE ALSO¶malloc(9), memguard(9)
|January 29, 2015||Linux 4.19.0-10-amd64|