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Posted to commits@cassandra.apache.org by "David Capwell (Jira)" <ji...@apache.org> on 2020/08/07 16:50:00 UTC
[jira] [Comment Edited] (CASSANDRA-16036) Add flag to disable chunk
cache and disable by defaul
[ https://issues.apache.org/jira/browse/CASSANDRA-16036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17172892#comment-17172892 ]
David Capwell edited comment on CASSANDRA-16036 at 8/7/20, 4:49 PM:
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The test performed was 11% read of slices on a clustering key, so 89% write; workload from prod.
What I saw in CPU profiles was that the chunk cache was a decent part of compaction and the read path, but not in a positive way. With compaction also populating the cache, it caused a constant churn from the cache, but all reads had to pay the cost for it.
was (Author: dcapwell):
The test performed was 11% read of slices on a clustering key, so 89% write; workload from prod.
What I was in the CPU profiles was that the chunk cache was a good chunk of compaction and the read path, but not in a positive way. With compaction also populating the cache, it caused a constant churn from the cache, but all reads had to pay the cost for it.
> Add flag to disable chunk cache and disable by defaul
> -----------------------------------------------------
>
> Key: CASSANDRA-16036
> URL: https://issues.apache.org/jira/browse/CASSANDRA-16036
> Project: Cassandra
> Issue Type: Bug
> Components: Legacy/Local Write-Read Paths
> Reporter: David Capwell
> Assignee: David Capwell
> Priority: Normal
> Fix For: 4.0-beta
>
> Attachments: Histogram-11.png
>
>
> Chunk cache is enabled by default and doesn’t have a flag to disable without impacting networking. In performance testing 4.0 against 3.0 I found that reads were slower in 4.0 and after profiling found that the ChunkCache was partially to blame; after disabling the chunk cache, read performance had improved.
> {code}
> 40_w_cc-selects.hdr
> #[Mean = 11.50063, StdDeviation = 13.44014]
> #[Max = 482.41254, Total count = 316477]
> #[Buckets = 25, SubBuckets = 262144]
> 40_wo_cc-selects.hdr
> #[Mean = 9.82115, StdDeviation = 10.14270]
> #[Max = 522.36493, Total count = 317444]
> #[Buckets = 25, SubBuckets = 262144]
> {code}
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