swapon, swapoff - start/stop swapping to file/device
#include <asm/page.h> /* to find PAGE_SIZE */
int swapon(const char *path, int swapflags);
int swapoff(const char *path);
swapon sets the swap area to the file or block device
specified by path. swapoff stops swapping to the file or
block device specified by path.
swapon takes a swapflags argument. If swapflags has the
SWAP_FLAG_PREFER bit turned on, the new swap area will
have a higher priority than default. The priority is
(prio << SWAP_FLAG_PRIO_SHIFT) & SWAP_FLAG_PRIO_MASK
These functions may only be used by the super-user.
Each swap area has a priority, either high or low. The
default priority is low. Within the low-priority areas,
newer areas are even lower priority than older areas.
All priorities set with swapflags are high-priority,
higher than default. They may have any non-negative value
chosen by the caller. Higher numbers mean higher prior
Swap pages are allocated from areas in priority order,
highest priority first. For areas with different priori
ties, a higher-priority area is exhausted before using a
lower-priority area. If two or more areas have the same
priority, and it is the highest priority available, pages
are allocated on a round-robin basis between them.
As of Linux 1.3.6, the kernel usually follows these rules,
but there are exceptions.
On success, zero is returned. On error, -1 is returned,
and errno is set appropriately.
Many other errors can occur if path is not valid.
EINVAL is returned if path exists, but is neither a regu
lar path nor a block device.
ENOENT is returned if path does not exist.
ENOMEM is returned if there is insufficient memory to
These functions are Linux specific and should not be used
in programs intended to be portable. The second
`swapflags' argument was introduced in Linux 1.3.2.
The partition or path must be prepared with mkswap(8).
mkswap(8), swapon(8), swapoff(8)