Vmstat output description

Vmstat output description

The output items are described as follows:
Procs
* The r column indicates the number of processes that run and wait for the cpu time segment. If the value is about the number of cpu resources in the system for a long time, the cpu is insufficient.
* Column B indicates the number of processes waiting for resources, such as waiting for IO or memory switching.

Memory
* The swap column indicates the memory size (in KB) for switching to the swap zone. If the value of swap is not 0 or is relatively large, As long as si and so are 0 for a long time, it is generally not a performance problem.
* The free column indicates the number of idle physical memory (in KB)
* The buff column indicates the memory size of the buffers cache. Generally, the buffer is required for reading and writing Block devices.
* The cache column indicates the page cached memory size, which is usually cached by the file system. files that are frequently accessed will be cached. If the cache value is large, there are many cached files. If the bi in io is small at this time, the file system is more efficient.

Swap
* The si column indicates the memory transferred from the disk, that is, the memory size from the memory to the memory swap zone, in KB/second.
* The so column indicates the size of memory transferred from the memory to the disk, that is, the size of memory transferred from the memory swap area, in KB/second.
In general, the si and so values are both 0. If the si and so values are not 0 for a long time, the system memory is insufficient and the system memory needs to be increased.
Io
Io items display disk read/write status
The bi column indicates the total amount of data read from the block device (that is, the disk is read) (kb/s)
The bo column indicates the total amount of data written to the block device (that is, the data written to the disk) (kb/s)
The reference value of bi + bo is 1000. If the value of bi + bo is greater than 1000 and the value of wa is large, it indicates that the system disk IO is faulty. You should consider improving the disk read/write performance.
System
Displays the number of interruptions during the collection interval.
The in column indicates the number of device interruptions per second observed during a certain interval.
Cs column indicates the number of context switches generated per second
The larger the two values above, the more CPU time consumed by the kernel.
CPU
Displays the CPU usage status, which is the focus of attention.
The us column shows the percentage of CPU time consumed by the user process. When the value of us is high, it indicates that the user process consumes a lot of CPU time, but if it is about 50% for a long time, you need to consider optimization algorithms or programs.
The sy column shows the percentage of CPU time consumed by kernel processes. When the sy value is high, it indicates that the kernel consumes a lot of CPU resources.
Based on experience, the reference value of us + sy is 80%. If us + sy is about 80%, there may be insufficient CPU resources.
The id column shows the percentage of time when the CPU is idle.
The wa column shows the percentage of CPU time occupied by IO wait. The higher the wa value, the more serious the IO wait. Based on experience, the reference value of wa is 20%. If wa exceeds 20%, the IO wait is serious. The cause of IO wait may be caused by a large number of random reads and writes on disks, it may also be caused by the bandwidth bottleneck of the disk or disk controller (mainly block operations.

To sum up, in the evaluation of CPU, pay attention to the value of the r column in procs item and the value of the us, sy, and id column in the CPU item.

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