Nick Puz created CASSANDRA-5506: ----------------------------------- Summary: Reduce memory consumption of IndexSummary Key: CASSANDRA-5506 URL: https://issues.apache.org/jira/browse/CASSANDRA-5506 Project: Cassandra Issue Type: Improvement Components: Core Affects Versions: 1.2.3 Reporter: Nick Puz
I am evaluating cassandra for a use case with many tiny rows which would result in a node with 1-3TB of storage having billions of rows. Before loading that much data I am hitting GC issues and when looking at the heap dump I noticed that 70+% of the memory was used by IndexSummaries. The two major issues seem to be: 1) that the positions are stored as an ArrayList<Long> which results in each position taking 24 bytes (class + flags + 8 byte long). This might make sense when the file is initially written but once it has been serialized it would be a lot more memory efficient to just have an long[] (really a int[] would be fine unless 2GB sstables are allowed). 2) The DecoratedKey for a byte[16] key takes 195 bytes -- this is for the overhead of the ByteBuffer in the key and overhead in the token. To somewhat "work around" the problem I have increased index_sample but will this many rows that didn't really help starts to have diminishing returns. NOTE: This heap dump was from linux with a 64bit oracle vm. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira