Monitoring Swap Resources
The /usr/sbin/swap command is used to manage swap areas. Two options, -l and
-s, display information about swap resources.
Use the swap -l command to identify a system's swap areas. Activated swap devices
or files are listed under the swapfile column.
# swap -l
swapfile dev swaplo blocks free
/dev/dsk/c0t0d0s1 136,1 16 1638608 1600528
Use the swap -s command to monitor swap resources.
# swap -s
total: 57416k bytes allocated + 10480k reserved = 67896k used,
The used value plus the available value equals the total swap space on
the system, which includes a portion of physical memory and swap devices (or
You can use the amount of available and used swap space (in
the swap -s output) as a way to monitor swap space usage over
time. If a system's performance is good, use swap -s to determine how much swap
space is available. When the performance of a system slows down, check the
amount of available swap space to determine if it has decreased. Then you
can identify what changes to the system might have caused swap space usage
When using this command, keep in mind that the amount of physical
memory available for swap usage changes dynamically as the kernel and user processes lock
down and release physical memory.
Note - The swap -l command displays swap space in 512-byte blocks. The swap -s command displays
swap space in 1024-byte blocks. If you add up the blocks from swap -l
and convert them to Kbytes, the result is less than used + available
(in the swap -s output). The reason is that swap -l does not include physical
memory in its calculation of swap space.
The output from the swap -s command is summarized in the following table.
Table 21-1 Output of the swap -s Command
amount of swap space in 1024-byte blocks that is currently allocated as backing
store (disk-backed swap space).
The total amount of swap space in 1024-byte blocks
that is not currently allocated, but claimed by memory for possible future use.
total amount of swap space in 1024-byte blocks that is either allocated or
The total amount of swap space in 1024-byte blocks that is currently available
for future reservation and allocation.