Understanding 'swap' output

In the good old days, swap meant only the "disk portion" of virtual memory. With recent additions and updates to the Solaris OS swap combines "traditional swap" & "unused RAM". In reality swap has now become the virtual memory.

Getting swap information is simple, but have you really looked at what the output is saying?

Using swap -s produces a summary of the vitual memory usage.

For example:

root@solaris# swap -s
total: 1124728k bytes allocated + 558824k reserved = 1683552k used, 15399632k available

In the above output, notice that all the values are in 1k units (1024 bytes).

Breaking down the output, we see:

• allocated — Amount of memory pages effectively used by processes written to virtual memory. From the about example:1124728k = 1.072 GB of virtual memory already in use.
• reserved — Amount of virtual memory not yet written to. From the above example:558824k = 0.532 GB of virtual memory is yet to be used.
• available — Virtual memory that can be provided to processes. For the about example:15399632k = 14.686 GB of virtual memory is available.