RHCE Learning Notes (19) priority of the process

This section studies the priority of the process and the setting of the nice value. In the case of high CPU load, high priority processes take precedence. RHEL7 priority = Priority coefficient +nice value to determine. The precedence factor can be seen as a static value for a kernel, so we can change the priority by resizing Nice. Nice's values range from 20 to 19, and the higher the number, the lower the priority. Nice defaults to 0

First change the CPU to a single core, so that it is easy to experiment, see Cpuinfo, is a single core

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Input top, can display the change of Cpu,nice value in real time

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Press and hold Ctrl+shift+t, open two more terminals, and then execute two dead loop commands, which will cause the CPU usage to rise continuously, pay attention to their PID number

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Inside the top window, you can see that CPU utilization is basically half-divided because their nice values are the default 0

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You can change the nice value by Renice command, note that you must use root permissions to change

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You can see that the nice value of 20 has the highest priority, so the CPU resources allocated to him are up to 95%

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This time has been a bit of a card, can be killall to terminate the process

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In addition, in the top window, the direct input R can also change Nice's, as shown below

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So how do you specify a nice value to run at the beginning, and you can prepend a value by adding nice-n to a normal command

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The value inside top is displayed as-10

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This article is from the "Mapo Tofu" blog, please be sure to keep this source http://beanxyz.blog.51cto.com/5570417/1602322

RHCE Learning Notes (19) priority of the process