vmstat command reports information about processes, memory, paging, block IO, traps, and cpu activity. However, a real advantage of vmstat command output – is to the point and (concise) easy to read/understand. The output of vmstat command use to help identify system bottlenecks. Please note that Linux vmstat does not count itself as a running process.
# vmstat -S m 4 5 procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 1 0 330 95 231 848 0 0 11 17 0 0 6 0 91 2 0 2 1 330 93 231 849 0 0 0 5493 1288 378 66 3 15 16 0 0 0 330 95 231 849 0 0 0 110 1035 105 15 1 83 2 0 0 0 330 97 231 849 0 0 0 919 1085 211 0 0 94 6 0 0 0 330 96 231 849 0 0 0 29 1036 99 0 0 99 1 0
Where,
* The fist line is nothing but six different categories. The second line gives more information about each category. This second line gives all data you need.
* -S M: vmstat lets you choose units (k, K, m, M) default is K (1024 bytes) in the default mode. I am using M since this system has over 4 GB memory. Without -M option it will use K as unit.
* 4 5 :4 is the delay between updates in seconds, and 5 is the number of updates.
Field Description For Vm Mode
- procs is the process-related fields are:
* r: The number of processes waiting for run time.
* b: The number of processes in uninterruptible sleep.
- memory is the memory-related fields are:
* swpd: the amount of virtual memory used.
* free: the amount of idle memory.
* buff: the amount of memory used as buffers.
* cache: the amount of memory used as cache.
- swap is swap-related fields are:
* si: Amount of memory swapped in from disk (/s).
* so: Amount of memory swapped to disk (/s).
- io is the I/O-related fields are:
* bi: Blocks received from a block device (blocks/s).
* bo: Blocks sent to a block device (blocks/s).
- system is the system-related fields are:
* in: The number of interrupts per second, including the clock.
* cs: The number of context switches per second.
- cpu is the CPU-related fields are:
These are percentages of total CPU time.
* us: Time spent running non-kernel code. (user time, including nice time)
* sy: Time spent running kernel code. (system time)
* id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
* wa: Time spent waiting for IO. Prior to Linux 2.5.41, shown as zero.
* st: Time stolen from a virtual machine. Prior to Linux 2.6.11, unknown.
