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more paging and swapping

more paging and swapping

In a recent post, someone mentioned that if po and pi from vmstat were < 5, very little page swapping was occuring.

On my system, I've got po and pi < 2 but:
re = 50
at = 12
fr = 24
avm = 229133

The physical memory useage is close to 88%.

Does this mean I have a lot of active swapping?
2 REPLIES
A. Clay Stephenson
Acclaimed Contributor

Re: more paging and swapping

Hi:

It's difficult to say from 1 vmstat snapshot. A better picture is a number of vmstat's taken over a period of time or vmstat -s which gives totals. In that case, are the number of page outs high.
My favorite way is to do a vmstat -z to zero the cumulatives, and then do a series of vmstat -s 's over a period of time. Page out's should be small; if not, your box is feeling some memory pressure. Page in's are not very important.

You should probably examine the dynamic buffer cache tunabales. Out of the box, dbc_max_pct is set to 50% and that is almost certainly too high. 10-15% is reasonable in most cases with min around 5%.


If it ain't broke, I can fix that.
Bill Hassell
Honored Contributor

Re: more paging and swapping

Even when memory is never fully used, there will some minor paging due to memory mapped files. The effect on the system's performance is minimal.


Bill Hassell, sysadmin