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Posted to commits@cassandra.apache.org by "David Capwell (Jira)" <ji...@apache.org> on 2021/02/25 23:46:00 UTC
[jira] [Updated] (CASSANDRA-16471)
org.apache.cassandra.io.util.DataOutputBuffer#scratchBuffer is around 50%
of all memory allocations
[ https://issues.apache.org/jira/browse/CASSANDRA-16471?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
David Capwell updated CASSANDRA-16471:
--------------------------------------
Change Category: Performance
Complexity: Low Hanging Fruit
Status: Open (was: Triage Needed)
> 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
> Priority: Normal
> 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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