Good evening,
I’m developing a java tcp server for communication between clients.
At this point i’m load testing the developed server.
This morning i got my hands on a profiler (yourkit) and started looking for problem spots in my server.
I now have 480 clients sending messages to the server every 500 msec. The server forwards every received message to 6 clients.
The server is now using about 8% of my cpu, when being on constant load.
My question is about the java functions that uses the most cpu cycles.
The java function that uses the most cpu cycles is strangly “Thread.sleep”, followed by “BufferedReader.readLine”.
Both of these functions seem to block the current thread while waiting for something (sleep waits for a few msec, readline waits for data).
Can somebody explain why these 2 functions take up that much cpu cycles? I was also wondering if there are alternative approaches that use less cpu cycles.
Kind regards,
T. Akhayo
sleep() and readLine() can use a lot of cpu as they both result in system calls which can context switch. It is also possible that the timing for these methods is not accurate for this reason (it may be an over estimate)
A way to reduce the overhead of context switches/sleep() is to have less threads and avoid needing to use sleep (e.g. use ScheduledExecutorServices), readLine() overhead can be reduced by using NIO but it is likely to add some complexity.