How to calculate CPU percentage

System administrators often face a difficult problem: quickly generate virtual CPU load on the machine. This article provides a simple and effective solution without installing additional tools.

Single-core CPU load:

The most basic method is to write a simple infinite loop program in C language. Just save the following code as a file (for example, stressme.c ), and compile and run:

 <code class="c">int main() {while (1) {}}</code>

Compile command: gcc -ostressme stressme.c (Linux/macOS) or cl stressme.c (Windows). Run the command: ./stressme (Linux/macOS) or stressme.exe (Windows). After the program is run, it will occupy 100% of the resources of a CPU core. In the case of multi-core, this program can be run multiple times.

Multi-core CPU load:

To occupy multiple cores at the same time, multi-threading can be used. The following code is implemented using 4 POSIX threads:

 <code class="c">#include <pthread.h> #include <unistd.h> #define num_threads 4 void *loop(void *arg) { while (1) {} } int main() { pthread_t threads[num_threads]; for (int i = 0; i </unistd.h></pthread.h></code>

Compile command: gcc -o multistress multistress.c -pthread (Linux/macOS).

How it works:

At the heart of these programs is an infinite loop ( while (1) {} ). After compilation, this will be translated into a simple assembly instruction jmp _start (jump to itself), which the CPU will continuously execute, thereby maximizing CPU resources. Modern operating systems adopt preemptive multitasking, allowing other processes to run, and even if these programs take up all CPU time, they can be terminated.

In old collaborative multitasking systems, this infinite loop could cause system crashes, but in modern systems it provides a simple and straightforward way to generate CPU load.

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