cpu usage: Describes the percentage of non-idle cpu cpu time, total time, according to the different tasks are divided into running, the user cpu usage, system cpu usage, io cpu usage, hard interrupt soft interrupt cpu usage
- User cpu usage: cpu process in user mode (user) and low-priority process (nice) cpu percentage of the total run time if the value is higher, then the user-mode processes have very busy.
- Cpu utilization system: cpu cpu percentage of the total running time in the kernel mode operation time, if the value is higher, then the kernel mode is very busy.
- io cpu utilization: cpu time waiting operation io cpu percentage of the total run time, if the value is higher, then the system and the long interaction time io devices.
- Hard interrupt soft interrupt cpu utilization: the percentage of cpu cores represent the total running time of hard time handling interrupts and soft interrupt routine takes, if the value is higher, usually it indicates the occurrence of a large number of system interruption.
- In addition to the above, as well as in a virtualized environment will be used to steal cpu usage (steal) and customer cpu usage (guest), respectively, other virtual machine takes cpu time percentage, and guest virtual machines running cpu time percentage.
Average load: that is, the average number of active system processes. It reflects the overall load of the system, there are three values, refer to the past 1 minute, 5 minutes, and the average load for 15 minutes, ideally, it is equal to the number of logical cpu average load, which means that each have just been fully cpu use. If the load is greater than the average number of logical cpu, it means a heavy load.
Process context switch:
Including: Unable to get resources resulting from voluntary context switches
Involuntary context is scheduled systems result in forced switching
Context switch itself is one of the core skills to ensure the normal operation of linux. But excessive context switching, will run the original process cpu time consumed in saving and restoring registers, the kernel stack, and virtual memory and other data, shorten the time to run a real process, become a performance bottleneck.