> So to resolve this i must tune young generation (HEAP_NEWSIZE) -Xmn, and > tune in_memory_compaction_limit_in_mb config parameter?
More likely adjust the initial occupancy trigger and/or the heap size. Probably just the latter. This is assuming you're on 0.7 with mostly default JVM options. See cassandra-env.sh. In fact, you may even be helped by *decreasing* the young generation size if you're running a version which has a cassandra-env which specifies -Xmn. I'm not entirely sure because I don't know off hand exactly based on what the occupancy trigger is happening, but the young gen is large and the workload is such that young-gen gc:s promote a high percentage of it's data, I suspect that can lead to CMS triggering too late. (So this paragraph is speculation.) -- / Peter Schuller
