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CONTIGMALLOC(9) 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 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 return NULL if 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(). Its use is depre- cated in favor of free(9) which no longer requires the caller to know the size and also accepts NULL as an address. 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 recla- mation 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 cross- ing 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) FreeBSD 14.3 July 22, 2024 CONTIGMALLOC(9)
NAME | SYNOPSIS | DESCRIPTION | IMPLEMENTATION NOTES | RETURN VALUES | EXAMPLES | DIAGNOSTICS | SEE ALSO
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