[CASSANDRA-3618] OpenBitSet can allocate more bytes than it needs

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 1.0.7
• Severity: Normal
• Assignee: Sylvain Lebresne
• Reporter: Sylvain Lebresne

Authors

Sylvain Lebresne

Reviewers

Jonathan Ellis

• Created: 13/Dec/11 00:52
• Updated: 16/Apr/19 09:32
• Resolved: 14/Dec/11 15:43

Description

CASSANDRA-2466 changed OpenBitSet to break big long arrays into pages. However, it always allocate full pages, each page being of size 4096 * 8 bytes. This means that we almost always allocate too much bytes, and for a row that has 1 column, the associated row bloom filter allocates 32760 more bytes than it should.

This has a significant impact on performance. In a small test using the SSTableSimpleUnsortedWriter to generate rows with 1 column, 0.8 is about twice as fast as 1.0 because of that (the difference shrink when there is more columns obviously).