The syslog-ng Administrator Guide

When syslog-ng is receiving messages from a large number of TCP or unix-stream connections, the CPU usage of syslog-ng might increase even if the number of messages is low. By default, syslog-ng processes every message when it is received. To reduce the CPU usage, process the incoming messages in batches. To accomplish this, instruct syslog-ng to wait for a short time before processing a message. During this period additional messages might arrive that can be processed together with the original message. To process log messages in batches, set the time_sleep() option (measured in milliseconds) to a non-zero value. Include the following line in your syslog-ng configuration:

	            
options { time_sleep(20); };	            
		

	Note
	It is not recommended to increase the time_sleep() parameter above 100ms, as that might distort timestamps, slow down syslog-ng, and cause messages to be dropped. When modifying the time_sleep() option, also adjust the log_fetch_limit() and log_fifo_size() options accordingly.

The max_connections() parameter limits the number of parallel connections for the source.

If adjusting the time_sleep() option is not desired for some reason, an alternative solution is to use unix-stream(), udp() and unix-dgram() sources instead of tcp() connections.