Hi, I am trying to investigate ParNew promotion failures happening routinely in production. As part of this exercise, I enabled -XX:PrintHistogramBeforeFullGC and saw the following output. As you can see there are a ton of Columns, ExpiringColumns and DeletedColumns before GC ran and these numbers go down significantly right after GC. Why are there so many expiring and deleted columns?
*Before GC:* num #instances #bytes class name ---------------------------------------------- 1: 113539896 5449915008 java.nio.*HeapByteBuffer* 2: 15979061 2681431488 [B 3: 36364545 1745498160 edu.stanford.ppl.concurrent.SnapTreeMap$Node 4: 23583282 754665024 org.apache.cassandra.db.*Column* 5: 8745428 209890272 java.util.concurrent.ConcurrentSkipListMap$Node 6: 5062619 202504760 org.apache.cassandra.db.*ExpiringColumn* 7: 45261 198998216 [I 8: 1801535 172947360 edu.stanford.ppl.concurrent.CopyOnWriteManager$COWEpoch 9: 1473677 169570040 [J 10: 4713304 113119296 java.lang.Double 11: 3246729 103895328 org.apache.cassandra.db.*DeletedColumn* *After GC:* num #instances #bytes class name ---------------------------------------------- 1: 11807204 1505962728 [B 2: 12525536 601225728 java.nio.*HeapByteBuffer* 3: 8839073 424275504 edu.stanford.ppl.concurrent.SnapTreeMap$Node 4: 8194496 262223872 org.apache.cassandra.db.*Column* cache.KeyCacheKey 17: 432119 17284760 org.apache.cassandra.db.*ExpiringColumn* 21: 351096 11235072 org.apache.cassandra.db.*DeletedColumn*
