Linux - Performance

Howto: determine LVM device in iostat output 

ls -l /dev/mapper/*

the device minor number corresponds to the dm-N number

Memory

Because the kernel does file caching the 'free' for 'buffers/cache' is actually what is available for use. 

$ free -m
             total       used       free     shared    buffers     cached
Mem:          4096       3757        338          0        869       1814
-/+ buffers/cache:       1074       3021
Swap:         4095          0       4095

Never look at the ouput from a single vmstat, those are averages over time and do not reflect current values. 

$ vmstat 1 3
sar
Memory: 
$ sar -r
Swap: 
$ sar -W
Paging: 
$ sar -B
Queue length and load average: 
$ sar -q
CPU utilization: 
$ sar -u
Per-processor: 
$ sar -P {cpu_num}

or 

$ sar -P ALL
Context switching: 
$ sar -w
I/O rates: 
$ sar -b
Per block device: 
$ sar -dp
Network: 
$ sar -n DEV
Historical data: 
$ sar {options} -f /var/log/sa/sa{dd}
swappiness

View/adjust kernel tendency to swap (larger is greater tendency).

To view: 

cat /proc/sys/vm/swappiness

Adjust on the fly: 

echo {number} > /proc/sys/vm/swappiness

Adjust permanently: