Reduce CPU usage of a running process: Unix Command [closed]

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I was trying to find a UNIX/Linux command to limit memory and CPU usage once I realize that a process is consuming 90% or more. So basically a command to reduce usage on a process that is already running without restarting the process. Thank you.

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nice (built-in) or cpulimit http://cpulimit.sourceforge.net/

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/usr/bin/ulimit or the shell builtin ulimit can be used when you launch the process to set resource limits. Not after the process is running. The nice command is run as the process owner BEFORE you run the image file. Not after

renice is the command used after the process has already started.

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I don't know how to set a hard limit on CPU usage. But you can force a process to be nicer to other processes with the renice command

renice -n 10 -p PID

where PID is the process id of the process whose priority you want to reduce.

What this does is tell the OS scheduler to reduce the process's priority, i.e. other processes that want to run get more of the CPU. man 1 renice has the details.