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CONTIGMALLOC(9)       DragonFly Kernel Developer's Manual      CONTIGMALLOC(9)


contigmalloc, contigfree -- manage contiguous kernel physical memory


#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);


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 type argument is ignored. The flags parameter modifies contigmalloc()'s behavior as follows: M_WAITOK Causes contigmalloc() to try flushing the active page queue in its second pass. Note that (unlike kmalloc(M_WAITOK)) contigmalloc(M_WAITOK) can still return NULL. M_ZERO Causes the allocated physical memory to be zero filled. Other flags (if present) are ignored. The contigfree() function deallocates memory allocated by a previous call to contigmalloc().


The contigmalloc() function does not sleep waiting for memory resources to be freed up, but instead scans available physical memory a small num- ber 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.


The contigmalloc() function returns a kernel virtual address if alloca- tion succeeds, or NULL otherwise.


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 cross- ing a 1M address boundary.


The contigmalloc() function will panic if size is zero, or if alignment or boundary is not a power of two.


kmalloc(9) DragonFly 4.7 January 19, 2008 DragonFly 4.7

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