Daemon Dancing in the Dark

Swap Market

How to find out if you are using swap? These days, you should have plenty of memory, even with the piggish apps we all use. So you might want to find out how often you are using the swap space, to see if it is time to splurge on a RAM. Well, it is vmstat to the rescue:

$ vmstat 5
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 1  2    204   4340  29984 140436    0    0   281   122  238  773 25  6 62  7
 1  2    204   5636  26188 139620    0    0  1612  3793 1111 1953  5  5  1 89
 0  2    204   8032  25420 133464    0    0  1516    30 1115 2342  6  6  0 87
 1  1    204   7020  26068 130084    0    0  1444    89 1042 2289 10  7  0 83
 0  1    204  13604  21472 129780    0    0  2158    65  937 1911 22 21  0 56
 1  2    204   5884  22888 127960    0    0  1640     2 1180 2495  8  7  2 83

The main column you want to look at is the swap 'so' column. This tells you the amount of memory 'swapped out'. In my case, it is zero, so we're looking good, although I only have 1gb of RAM. I still think I'll grab another gigabyte. The '5' means to update the status every 5 seconds. And the first line shows the average of all the numbers since the machine was last rebooted, which is cool. As I've taken to shutting down all my machines every night, it isn't as interesting as it would have been a month ago, when the machine would run for weeks at a time.

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