Many AIX users are facing troubles during actual memory usage in IBM servers. But the below simple calculation may reduce your doubts.
The command svmon -G can be used to determine the actual memory consumption of a server. To determine if the memory is over-committed, you need to divide the memory-virtual value by the memory-size value, e.g.:
bash-4.2# svmon -G
size inuse free pin virtual mmode
memory 8388608 8357353 31255 1831582 6924332 Ded
pg space 4325376 29713
work pers clnt other
pin 1577710 0 0 253872
in use 6924332 5 1433016
PageSize PoolSize inuse pgsp pin virtual
s 4 KB - 2981497 29713 337742 1548476
m 64 KB - 335991 0 93365 335991
bash-4.2#
In this example, the memory-virtual value is 6924332, and the memory-size value is 5079040. Note that the actual memory-inuse (8388608) is nearly the same as the memory-size (5079040) value. This is simply AIX caching as much as possible in its memory. Hence, the memory-free value is typically very low, 31255 in the example above. As such, determining the memory size based on the memory-free value does not provide a good interpretation of the actual memory consumption, as memory typically includes a lot of cached data.
Now, to determine the actual memory consumption, divide memory-virtual by memory-size:
# bc
scale=2
6924332/8388608
.82
Thus, the actual memory consumption is 82% of the memory. The size of the memory is 8388608 blocks of 4 KB = 2097152 MB. The free memory is thus: (100% - 82%) * 2097152 MB = 37748736 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.
The command svmon -G can be used to determine the actual memory consumption of a server. To determine if the memory is over-committed, you need to divide the memory-virtual value by the memory-size value, e.g.:
bash-4.2# svmon -G
size inuse free pin virtual mmode
memory 8388608 8357353 31255 1831582 6924332 Ded
pg space 4325376 29713
work pers clnt other
pin 1577710 0 0 253872
in use 6924332 5 1433016
PageSize PoolSize inuse pgsp pin virtual
s 4 KB - 2981497 29713 337742 1548476
m 64 KB - 335991 0 93365 335991
bash-4.2#
In this example, the memory-virtual value is 6924332, and the memory-size value is 5079040. Note that the actual memory-inuse (8388608) is nearly the same as the memory-size (5079040) value. This is simply AIX caching as much as possible in its memory. Hence, the memory-free value is typically very low, 31255 in the example above. As such, determining the memory size based on the memory-free value does not provide a good interpretation of the actual memory consumption, as memory typically includes a lot of cached data.
Now, to determine the actual memory consumption, divide memory-virtual by memory-size:
# bc
scale=2
6924332/8388608
.82
Thus, the actual memory consumption is 82% of the memory. The size of the memory is 8388608 blocks of 4 KB = 2097152 MB. The free memory is thus: (100% - 82%) * 2097152 MB = 37748736 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.
No comments:
Post a Comment