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https://issues.apache.org/jira/browse/CASSANDRA-16036?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jon Meredith updated CASSANDRA-16036:
-------------------------------------
Reviewers: Jon Meredith, Jon Meredith (was: Jon Meredith)
Jon Meredith, Jon Meredith
Status: Review In Progress (was: Patch Available)
I took a first pass through. I definitely think we should be able to disable
the {{ChunkCache}} without impacting the \{{BufferPool}} and seem like they
should be two separate configuration entries to me.
The code changes look good too.
The only thing that needs more discussion is the change to make the ChunkCache
be disabled by default. A single benchmark isn't enough evidence to convince
me.
We could either leave the default as enabled (in which case I think it's
already good to go once CI is happy), or if we are able to collect a few more
benchmarks (read-heavy, write-heavy, compaction-heavy, hot-key) to justify
disabling then we should do so.
> 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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