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 encoded as:
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
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
Swap pages are allocated from areas in priority order, highest priority first.
For areas with different priorities, 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