[CASSANDRA-17402] Unshared heap size excluding data calculation is broken

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 4.0.4, 4.1-alpha1, 4.1
• Component/s: Local/Memtable
• Bug Category: Correctness
• Severity: Normal
• Complexity: Low Hanging Fruit
• Discovered By: Code Inspection
• Platform: All
• Since Version: 4.0.2

Source Control Link

https://github.com/apache/cassandra/commit/a690f339ab0f2b98c69621ca5a0bad10ae9a7919

Test and Documentation Plan

The the regression and new tests

• Assignee: Jacek Lewandowski
• Reporter: Jacek Lewandowski

Authors

Jacek Lewandowski

Reviewers

Andres de la Peña, Branimir Lambov

• Created: 24/Feb/22 09:57
• Updated: 27/May/22 19:24
• Resolved: 07/Mar/22 16:36

Description

Unshared heap size excluding data calculation is broken.

For example, it does not takes into consideration whether the buffers are on-heap or off-heap - empty offheap buffer is 64-bytes while empty heap buffer is 48-bytes.

It matters especially when we have offheap buffers-based memtables.

Issue Links

• is caused by: CASSANDRA-16900 org.apache.cassandra.db.rows.ArrayCell#unsharedHeapSizeExcludingData includes data twice