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https://issues.apache.org/jira/browse/CASSANDRA-16036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17175741#comment-17175741
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David Capwell commented on CASSANDRA-16036:
-------------------------------------------
Added a read only workload; select = with chunk cache, select-2 is without
chunk cache. What I see is up to 99% they are equal, after with chunk cache
has an advantage, then at 99.99 without chunk cache has the advantage.
{code}
selects.hdr
#[Mean = 49.88099, StdDeviation = 37.74398]
#[Max = 1826.77504, Total count = 2880010]
#[Buckets = 25, SubBuckets = 262144]
selects-2.hdr
#[Mean = 51.66994, StdDeviation = 44.94572]
#[Max = 1810.85798, Total count = 2880036]
#[Buckets = 25, SubBuckets = 262144]
{code}
The mean has a diff of about 1ms.
> 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, Histogram-15.png, latency_selects.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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