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Calulation of SWAP Sapce utilization metric

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Occasional Contributor

Calulation of SWAP Sapce utilization metric



I am using GBL_SWAP_SPACE_UTIL to monitor Swap space utilization on servers with threshold as 95%. When an alert was generated for threshold breach on one of our Sun OS server , i logged to that particular server and run the top copmmand to check the swap utilization. Surprise to found that Swap utilization was 0% with below values


32G total swap, 32G free swap, 0.0% swap.

Even i check in Performance Manager which shows the value greater than 95%.


Please let me know how if the metric is calculation wrong value or thr is some caluculation whihc I am missing here.

I verified this on other few Sun servers as well but the same caluuclation issue.


Please help me to understand this swap utilization calculation metric as our Unix team is questioning us.




Honored Contributor

Re: Calulation of SWAP Sapce utilization metric

Hello Sagar,

On windows it uses GlobalMemoryStatus() API but i am not sure if same API is avilable for UNIX or not.

Hope you get better answer.

Honored Contributor

Re: Calulation of SWAP Sapce utilization metric

Below is what i found for UNIX.



The percent of available swap space that was being used by running processes

in the interval.

On HP-UX, swap space must be reserved (but not allocated) before virtual

memory can be created. If all of available swap is reserved, then no new

processes or virtual memory can be created. Swap space locations are

actually assigned (used) when a page is actually written to disk or locked in

memory (pseudo swap in memory). This is the same as (PCT USED: total) as

reported by the "swapinfo -mt" command.

On Unix systems, this metric is a measure of capacity rather than

performance. As this metric nears 100 percent, processes are not able to

allocate any more memory and new processes may not be able to run. Very low

swap utilization values may indicate that too much area has been allocated to

swap, and better use of disk space could be made by reallocating some swap

partitions to be user filesystems.

On Unix systems, this metric is updated every 30 seconds or the sampling

interval, whichever is greater.

On Solaris non-global zones, this metric is N/A.

On AIX System WPARs, this metric is NA.


Occasional Contributor

Re: Calulation of SWAP Sapce utilization metric

Thanks KAKA for your reply.


Went through the perfmon metric defination for GBL_SWAP_SPACE_UTIL for SUN OS and found that it is using the ouptu of swap -s command to caluculate the values. Not the values showing in top command.


And the values calculated from swap -s command is matching with the GBL_SWAP_SPACE_UTIL.

So this is fine now.



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