![]() ![]() I/O Wait is when the CPU is waitingįor an I/O operation to complete, and the CPU can’t be used for anything else. Aįile server for example would nearly spend all it’s life waiting for disk I/O Wait: Sometimes the CPU has only one thing to do – wait for the.Nice is when the CPU is executing a user task having Report generation process at a lower priority and interactive processes at Nice: The user code can be executed in “normal” priority, or variousĭegrees of “below normal” priority.The categorization could stop here, but there a few more, to provide better It actually goes to sleep while the kernel performs that work, and wakes up ![]() Note that if an application tries to read from disk or write to network, User: The CPU is running code in user-mode.System: The CPU is running kernel code. ![]() So what “types of tasks” are there? The obvious ones are “user” and “system”: Should really be using the value of sysconf(_SC_CLK_TCK) instead. Note: Technically the magic number 1/100 may be different for your system – you These counters are maintained by the kernel itself, and can be read from the If a CPU executes userĬode for 1 second, it’s user-code-counter will get incremented by 100. Particular task type, that counter is incremented. Maintained, so that while sampling if you see that a CPU is executing a Noting down what type of task each one is executing. Now imagine someone taking a look at all the CPUs every 1/100th of a second, and Independently schedulable execution unit. In Linux, the hyperthread is the most granular, Physical processors in a machine, each with multiple cores, and each core with In this context, a single CPU refers to a single (possibly ![]() CPU Usage is a picture of how the processors in your machine (real or virtual) ![]()
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