David Capwell created CASSANDRA-16471:
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Summary:
org.apache.cassandra.io.util.DataOutputBuffer#scratchBuffer is around 50% of
all memory allocations
Key: CASSANDRA-16471
URL: https://issues.apache.org/jira/browse/CASSANDRA-16471
Project: Cassandra
Issue Type: Improvement
Components: Local/Caching
Reporter: David Capwell
Assignee: David Capwell
Attachments: Screen Shot 2021-02-25 at 3.34.28 PM.png
While running workflows to compare 3.0 with trunk we found that allocations and
GC are significantly higher for a write mostly workload (22% read, 3% delete,
75% write); below is what we saw for a 2h run
Allocations
30: 1.64TB
40: 2.99TB
GC Events
30: 7.39k events
40: 13.93k events
When looking at the allocation output we saw the follow for memory allocations
Here we see that org.apache.cassandra.io.util.DataOutputBuffer#expandToFit is
around 52% of the memory allocations. When looking at this logic I see that
allocations are on-heap and constantly throw away the buffer (as a means to
allow GC to clean up).
With the patch, allocations/gc are the following
Allocations
30: 1.64TB
40 w/ patch: 1.77TB
40: 2.99TB
GC Events
30: 7.39k events
40 w/ patch: 8k events
40: 13.93k events
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