Copyright (c) 2004 Joseph Koshy
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$FreeBSD: head/share/man/man9/contigmalloc.9 171503 2007-07-19 17:23:20Z alc $

.Dd July 19, 2007 .Dt CONTIGMALLOC 9 .Os .Sh NAME .Nm contigmalloc , contigfree .Nd manage contiguous kernel physical memory .Sh SYNOPSIS n sys/types.h n sys/malloc.h .Ft "void *" .Fo contigmalloc .Fa "unsigned long size" .Fa "struct malloc_type *type" .Fa "int flags" .Fa "vm_paddr_t low" .Fa "vm_paddr_t high" .Fa "unsigned long alignment" .Fa "unsigned long boundary" .Fc .Ft void .Fo contigfree .Fa "void *addr" .Fa "unsigned long size" .Fa "struct malloc_type *type" .Fc .Sh DESCRIPTION The .Fn contigmalloc function allocates .Fa size bytes of contiguous physical memory that is aligned to .Fa alignment bytes, and which does not cross a boundary of .Fa boundary bytes. If successful, the allocation will reside between physical addresses .Fa low and .Fa high . The returned pointer points to a wired kernel virtual address range of .Fa size bytes allocated from the kernel virtual address (KVA) map.

p The .Fa flags parameter modifies .Fn contigmalloc Ns 's behaviour as follows: l -tag -width indent t Dv M_ZERO Causes the allocated physical memory to be zero filled. t Dv M_NOWAIT Causes .Fn contigmalloc to return .Dv NULL if the request cannot be immediately fulfilled due to resource shortage. .El

p Other flags (if present) are ignored.

p The .Fn contigfree function deallocates memory allocated by a previous call to .Fn contigmalloc . .Sh IMPLEMENTATION NOTES The .Fn contigmalloc function does not sleep waiting for memory resources to be freed up, but instead actively reclaims pages before giving up. However, unless .Dv M_NOWAIT is specified, it may select a page for reclamation that must first be written to backing storage, causing it to sleep. .Sh RETURN VALUES The .Fn contigmalloc function returns a kernel virtual address if allocation succeeds, or .Dv NULL otherwise. .Sh EXAMPLES d -literal void *p; p = contigmalloc(8192, M_DEVBUF, M_ZERO, 0, (1L << 22), 32 * 1024, 1024 * 1024); .Ed

p 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. .Sh DIAGNOSTICS The .Fn contigmalloc function will panic if .Fa size is zero, or if .Fa alignment or .Fa boundary is not a power of two. .Sh SEE ALSO .Xr malloc 9 , .Xr memguard 9