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contigmalloc.9freebsd

Langue: en

Version: 309551 (debian - 07/07/09)

Section: 9 (Appels noyau Linux)


BSD mandoc

NAME

contigmalloc , contigfree - manage contiguous kernel physical memory

SYNOPSIS

In sys/types.h In 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  

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.

The Fa flags parameter modifies Fn contigmalloc Ns 's behaviour as follows:

M_ZERO
Causes the allocated physical memory to be zero filled.
M_NOWAIT
Causes Fn contigmalloc to return NULL if the request cannot be immediately fulfilled due to resource shortage.

Other flags (if present) are ignored.

The Fn contigfree function deallocates memory allocated by a previous call to Fn contigmalloc .

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 M_NOWAIT is specified, it may select a page for reclamation that must first be written to backing storage, causing it to sleep.

RETURN VALUES

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

SEE ALSO

malloc(9), memguard(9)
L'homme n'est ni ange ni bête,
et le malheur veut que qui veut faire l'ange fait la bête.
-+- Blaise Pascal (1623-1662), Pensées VI.358 -+-