I am trying to parse some logs by logstash which is reading logs directly from a log file. While starting logstash using bin/logstash -f <config_file> logstash cpu usage go high(up to 80%). After some time logstash cpu become stable. But when logs are written into file and logstash parses logs, worker thread uses upto 40% of cpu.
In filter section of config file, I am using mutilline plugin also. It also contains 1 grok and 1 mutate filter per log.
What could be possible reason for high CPU usage?