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CONTIGMALLOC (9) | Kernel routines | Unix Manual Pages | :man

NAME

contigmalloc, contigfree - manage contiguous kernel physical memory

CONTENTS

Synopsis
Description
Implementation Notes
Return Values
Examples
Diagnostics
See Also

SYNOPSIS


.In sys/types.h
.In sys/malloc.h "void *"
.Fo contigmalloc "unsigned long size" "struct malloc_type *type" "int flags" "vm_paddr_t low" "vm_paddr_t high" "unsigned long alignment" "unsigned long boundary"
.Fc void
.Fo contigfree "void *addr" "unsigned long size" "struct malloc_type *type"
.Fc

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 flags parameter modifies contigmalloc ’s behaviour as follows:

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.

IMPLEMENTATION NOTES

The contigmalloc function does not sleep waiting for memory resources to be freed up, but instead scans available physical memory a small number 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.

RETURN VALUES

The contigmalloc function returns a kernel virtual address if allocation 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 address 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)


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