free virtual memory
vmstat <some nunmber in seconds>
swp: virtual mem used
free: idle mem
buff: used for buffers


info proc directory
# cat /proc/meminfo
        total:    used:    free:  shared: buffers:  cached:
Mem:  261337088 256851968  4485120  3145728  3407872 215240704
Swap: 526409728 145178624 381231104
MemTotal:       255212 kB
MemFree:          4380 kB
MemShared:        3072 kB
Buffers:          3328 kB
Cached:         178048 kB
SwapCached:      32148 kB
Active:         167568 kB
Inact_dirty:     48612 kB
Inact_clean:       416 kB
Inact_target:    13892 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       255212 kB
LowFree:          4380 kB
SwapTotal:      514072 kB
SwapFree:       372296 kB
NrSwapPages:     93074 pages

Command: free
# free
             total       used       free     shared    buffers     cached
Mem:        255212     248924       6288       3072       3380     175800
-/+ buffers/cache:      69744     185468
Swap:       514072     141776     372296





See also Sparc_linux