[ https://issues.apache.org/jira/browse/CASSANDRA-5020?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Benedict resolved CASSANDRA-5020. --------------------------------- Resolution: Not a Problem This has most likely become "not a problem" as a result of movement towards off-heap memtables + cells, which bring the overheads down as low as we can go with a per-cell data structure. > Time to switch back to byte[] internally? > ----------------------------------------- > > Key: CASSANDRA-5020 > URL: https://issues.apache.org/jira/browse/CASSANDRA-5020 > Project: Cassandra > Issue Type: Improvement > Components: Core > Reporter: Jonathan Ellis > Assignee: T Jake Luciani > Labels: performance > Fix For: 3.0 > > > We switched to ByteBuffer for column names and values back in 0.7, which gave > us a short term performance boost on mmap'd reads, but we gave that up when > we switched to refcounted sstables in 1.0. (refcounting all the way up the > read path would be too painful, so we copy into an on-heap buffer when > reading from an sstable, then release the reference.) > A HeapByteBuffer wastes a lot of memory compared to a byte[] (5 more ints, a > long, and a boolean). > The hard problem here is how to do the arena allocation we do on writes, > which has been very successful in reducing STW CMS from heap fragmentation. > ByteBuffer is a good fit there. -- This message was sent by Atlassian JIRA (v6.2#6252)