why does Jetty not use all allocated memory?

Question

we develop the webapp with Grails. In productio the webapp runs on Jetty. We used JMeter to run performance-test and yourkit to analyse the memory consumtion of jetty.

We started Jetty with params -Xms1500m -Xmx1500m, so in yourkit we can also see the allocated memory is about 1,5gb. But Jetty does not use it all, all time always about 300 - 500m and delivers bad performance. can serve only few requests/s.

• CPU ist not full loaded, all times only about 50%
• Jetty is running with default settings, 6.1.21 is used
• MySQL queries are simple, DB size is small and runs on the same machine as Jetty, could not be the problems
• Logs r written over FileAppender to HDD
• JMeter produces enought requests
• Yourkit shows the number of live threads is about 60

so how can we force jetty to use all allocated memory for better performance?

Thx you very much!

Answer 1

The problem is probably not the memory, it looks like you have enough.

You have probably other points of contention, for example exclusive-locks.

I suggest you take several snapshots of your threads, to examine where they are stuck. You should find the contention.