How to limit cpu usage for a terminal command that works on m1 mac and macOS Monterey?

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05-10-2024

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Taming the CPU Beast: Limiting Command Usage on Your M1 Mac

Running a CPU-intensive terminal command on your M1 Mac can lead to a frustratingly slow system or even a complete freeze. Luckily, there are ways to control the amount of processing power a command can utilize, ensuring a smoother workflow and preventing your computer from overheating.

The Scenario: You're running a demanding command in your terminal, like compiling a large project or processing extensive data. This command takes forever and your Mac feels sluggish. The fan roars, and you fear your system might crash.

Original Code:

# Example: Compiling a large project with a CPU-intensive command
make -j8 

Solution:

The key is to harness the power of nice, a command-line utility that modifies the priority of a process. By increasing the nice value, you can lower the priority of your command, allowing other processes to utilize more CPU time.

Here's how to limit CPU usage:

1. Use nice to adjust priority:

   nice -n 10 make -j8 
   

   • -n 10 sets the nice value to 10, decreasing the command's priority. A higher nice value means lower priority.
   • You can adjust the value from 0 to 19, with 0 being the highest priority and 19 the lowest.

2. Alternatively, use renice to adjust priority of an already running process:

   ps aux | grep make  # Find the process ID (PID) of the 'make' command
   renice -n 10 <PID>   # Set the nice value for the process with the specified PID
   

   • This approach is useful if you need to lower the priority of a process that is already running.

Additional Tips:

• Monitor your system: Use tools like top or htop to monitor CPU usage in real-time and adjust the nice value accordingly.
• Experiment: The optimal nice value might vary depending on your command and hardware. Start with a higher value (like 10 or 15) and gradually decrease it until you achieve a balance between performance and system responsiveness.
• Utilize other methods: You can also consider tools like cpulimit or taskset for more granular control over CPU usage.

Benefits:

• Smoother workflow: Avoid system sluggishness and slowdowns.
• Reduced overheating: Lower CPU load prevents your Mac from overheating and potential damage.
• Better resource management: Allow other applications to utilize more CPU time.

Example:

Let's say you're running a computationally intensive image processing script that takes hours to complete. You can use nice to limit its CPU usage, ensuring your Mac remains usable for other tasks.

nice -n 15 python process_images.py 

By applying these techniques, you can effectively manage CPU usage on your M1 Mac, preventing system overload and ensuring a smoother user experience. Remember, finding the right balance between performance and resource usage depends on your individual needs and workload. Experiment and adjust your settings accordingly for the best results.