FAQ: How do you measure swap utilization in FreeBSD?
Q: How do you measure swap utilization in FreeBSD? (Assuming you are writing a script to gather performance metrics.)
A: If you are writing a C program, check kvm_getswapinfo(3) and maybe take a gander at the bottom of /usr/src/usr.bin/top/machine.c.
A: If you are writing a Perl script:
Measure swap activity:
sysctl vm.stats.vm.v_swapin vm.stats.vm.v_swapout vm.stats.vm.v_swappgsin vm.stats.vm.v_swappgsout
(I believe these results are COUNTER type values, like you get from netstat -inb. You could establish “swap activity” by plotting changes in this value.)
Measure swap size:
0-13:38 djh@mito ~> swapinfo Device 1K-blocks Used Avail Capacity /dev/ad0s1b 1022224 0 1022224 0% 0-13:38 djh@mito ~> swapctl -l Device: 1024-blocks Used: /dev/ad0s1b 1022224 0
If you are trying to accomodate n+1 swap devices, try this:
0-13:44 djh@mito ~> swapctl -lsk Device: 1024-blocks Used: /dev/ad0s1b 1022224 0 Total: 1022224 0
