When looking vmstat, this is what I got: procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 1 0 0 2872 0 0 0 0 8 17 0 14 3 1 94 2 0 the cache is 0. I have no idea how much the whole swap I have. But when not enough RAM (256 MB), the swap will be used and look like below: procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 3 1 2468 0 0 0 0 0 8 17 0 16 3 1 94 2 0