How do I monitor memory swap activity?
When the system is under memory pressure, the pageout process reuses memory from the free, cache, inact and, if necessary, active pages. You can monitor the swap activity by viewing the syslog message reported by the kernel during periods of high pageout activity. The syslog message appears as follows:
Mar 3 20:08:02 olympic /kernel: High pageout rate!! 277 pages/sec.
You can use the vmstat –s command to print the statistics for the swapout activity. The displayed statistics appear as follows:
0 swap pager pageouts
0 swap pager pages paged out
The swap pager pageouts is the number of pageout operations to the swap device, and the swap pager pages paged out is the number of pages paged out to the swap device.
For more information, see Junos OS Routing Protocols Library for Routing Devices