swap areas

[Javier Ortiz Guajardo]

I have a question, how can I know if my system is't swaping to disc?
What can you say to me referring information to Pages in - Pages out ?

[Steven E. Protter · Accepted solution]

I'd also check swapinfo

vmstat po column does the job for us too.

SEP

[A. Clay Stephenson]

If you don't have Glance then run vmstat and only pay attention to the 'po' (page out) column. If this value is more than a very small value then you are swapping. Some po's can be attributed to memory-mapped files but if you are seeing significant po rates then you are definitely swapping. For all intents and purposes, pi's (page in's) can be ignored. Every time a new process is started, pi's occur.

[Sridhar Bhaskarla]

Hi Javier,

Do a swapinfo -t

Observe the 3rd column (KB Used) only for the dev|fs columns. Do not count the mem line if you have. If it is 0, then you are not swapping. If it is non-zero, then there is something paged out sitting on your swap. If the number is significant, then time for you to add more memory.

If it is non-zero, then do vmstat 2 5 and observe the po column. If it is a number, then you are most likely paging out. This in conjunction with swapinfo can give you a beter idea. Otherwise, you may get confused with memory mapped paging.

-Sri

[Chris Vail]

One of the confusing things about the vmstat command is the PI column, or pages swapped in. If your system is running Oracle, and your database has a lot of stored procedures, this is normal. Unless the stored procedure is used frequently, it is fairly soon swapped out to disk. Increasing the SGA (System Global Area) will decrease this somewhat. But even a fairly high PI (2-10/sec) is little to be concerned about. When that number gets too high, and stays too high, then its time to increase the amount of RAM in the system, and enlarge the SGA.

The PO column is of much more interest: a lot of entries here means that your application is starved for RAM. You can have a 2-10 number in the PI column as long as there is a small number (less than 5) in the PO column. A really efficient system would not have any entry at all in the PO column.


Chris