IBM AIX - Memory Consumption

IBM AIX - Memory Consumption

The command svmon -G can be used to determine the actual memory consumption of a server. To determine if the memory is overcommitted, you need to divide the memory-virtual value by the memory-size value, e.g.:

# svmon -G size inuse free pin virtual memory 5079040 5076409 2631 706856 2983249 pg space 7864320 12885 work pers clnt other pin 540803 0 2758 163295 in use 2983249 0 2093160 PageSize PoolSize inuse pgsp pin virtual s 4 KB - 4918761 12885 621096 2825601 m 64 KB - 9853 0 5360 9853

In this example, the memory-virtual value is 2983249, and the memory-size value is 5079040. Note that the actual memory-inuse is nearly the same as the memory-size value. This is simply AIX caching as much as possible in its memory. Hence, the memory-free value is typically very low.

Now, to determine the actual memory consumption, devide memory-virtual by memory-size:

# bc scale=2 2982321/5079040 .58

Thus, the actual memory consumption is 58% of the memory (5079040 blocks of 4 KB = 19840 MB). The free memory is thus: (100% - 58%) * 19840 MB = 8332 MB.

Try to keep the value of memory consumption less than 90%. Above that, you will generally start seeing paging activity using the vmstat command. By that time, it is a good idea to lower the load on the system or to get more memory in your system.