Minor GC pause times are too higfh. possible reasons?

I Am experiencing a regular high minor GC pause times(~ 9seconds).

The application is a server written in Java, executing 3 transactions/seconds.

Eventhough there’s no I/O excessive activity

Heap parameters are:

-Xms1G
-Xmx14G
-XX:+UseConcMarkSweepGC
-XX:+DisableExplicitGC
-XX:+PrintGC
-XX:+PrintGCApplicationStoppedTime
-XX:+PrintGCTimeStamps
-XX:+PrintGCDateStamps
-XX:+PrintGCDetails

What are the possible reasons for such minor gc pause times values?

Answer

As the other answer says, without GC log snippets it’s not possible to answer this definitively. Some things to think about:

Assuming no impact from the underlying OS (scheduling, CPU thrashing), the time taken for a minor collection will be proportional to the amount of live data in the young gen. when the collector runs (every live object in the young gen. gets copied during a minor GC). Looking at the graph of your old gen. you are seeing consistent growth which would indicate you are promoting significant amounts of data during minor GC. You’re either creating a lot of long-lived objects or you’re maintaining references unnecessarily.

To reduce the pauses you could try reducing the size of the Eden space (so there is less potential data to copy on each minor GC) and also reduce the tenuring threshold so that objects get moved out of the survivor spaces more quickly. The downside of this will be your minor GCs will happen more frequently so you will probably see a degradation in throughput.

I would also change the -Xms value. You clearly need more than 1Gb in your heap so it would be best to set it to 14Gb to avoid the heap having to be resized by the JVM as the amount of data increases.