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CONTIGMALLOC(9) BSD Kernel Developer's Manual CONTIGMALLOC(9) 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 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 contigmalloc_domainset() variant allows the caller to additionally specify a numa(4) domain selection policy. See domainset(9) for some ex- ample 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 return NULL if the request cannot be im- mediately 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 reclama- tion that must first be written to backing storage, causing it to sleep. The contigfree() function does not accept NULL as an address input, un- like free(9). RETURN VALUES The contigmalloc() function returns a kernel virtual address if alloca- tion 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 ad- dress 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. SEE ALSO malloc(9), memguard(9) BSD October 30, 2018 BSD
NAME | SYNOPSIS | DESCRIPTION | IMPLEMENTATION NOTES | RETURN VALUES | EXAMPLES | DIAGNOSTICS | SEE ALSO
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