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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Created] (CASSANDRA-5020) Time to switch back to byte[] internally?
Date Mon, 03 Dec 2012 17:09:59 GMT
Jonathan Ellis created CASSANDRA-5020:

             Summary: Time to switch back to byte[] internally?
                 Key: CASSANDRA-5020
             Project: Cassandra
          Issue Type: Improvement
          Components: Core
            Reporter: Jonathan Ellis
             Fix For: 1.3

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.

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