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Posted to commits@cassandra.apache.org by "David Capwell (Jira)" <ji...@apache.org> on 2020/08/07 20:13:00 UTC
[jira] [Commented] (CASSANDRA-16036) Add flag to disable chunk
cache and disable by default
[ https://issues.apache.org/jira/browse/CASSANDRA-16036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17173446#comment-17173446 ]
David Capwell commented on CASSANDRA-16036:
-------------------------------------------
[~jasonstack] was hoping I could get your feedback on this patch? From my testing, if there are writes going on the cluster the cache hit ratio tanks and chunk cache gets more costly than having it disabled; most workloads I see are write heavy, hence the default I went with.
> Add flag to disable chunk cache and disable by default
> ------------------------------------------------------
>
> 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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