Community:Modifying the splunk-search process priority
From Splunk Wiki
You can change the priority of a particular splunk-search process to reduce the impact of a long-running search. For more on the renice command (Unix systems) see its man page on your host.
You will need the pid for the desired process. Go to the jobs endpoint with a browser
to find the search id for your search. Then use ps to get the pid for the splunk-search process with the correct sid.
Note that you can only change the priority of a process as the user who owns that process or root.