2023-05-11

Ways to force or ask a process to use less cpu.
Here we show calling at the start of a new process. 
Another option (with some commmands) is to run the command on the pid of an already existing process. 


# "-i":include-childprocesses, VALUE can be e.g. 30 or 400 (4 cores) etc
cpulimit  -l VALUE% -i -v  CMD..ARGS

# bind process to specific core(s) 
taskset -c 0,2  CMD..ARGS 

# systemd-dependent, might need privilege 
systemd-run --scope -p AllowedCPUs=CPUNUMBER CMD..ARGS 
systemd-run --scope -p CPUQuota=VALUE% CMD..ARGS

# in the case of ffmpeg, the '-threads N' option can affect different parts of the 
# process, e.g. just decoding, or just video encoding, filtering, etc.; specifying 
# multiple times may be useful if wanting to limit several of these
ffmpeg -threads 1 -i $IN -filter:v fps=25 -vf  -threads 1 $OUT