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 speci-
fied 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 encoded as:
(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 priority.
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.
EPERM The user is not the super-user, or more than
MAX_SWAPFILES (defined to be 8 in Linux 1.3.6) are
EINVAL is returned if path exists, but is neither a regular
path nor a block device.
ENOENT is returned if path does not exist.
ENOMEM is returned if there is insufficient memory to start
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)