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https://issues.apache.org/jira/browse/CASSANDRA-15229?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Benedict updated CASSANDRA-15229:
---------------------------------
         Severity: Normal
       Complexity: Challenging
    Discovered By: Code Inspection
     Bug Category: Parent values: Degradation(12984)Level 1 values: Performance 
Bug/Regression(12997)
      Component/s: Local/Caching
           Status: Open  (was: Triage Needed)

> BufferPool Regression
> ---------------------
>
>                 Key: CASSANDRA-15229
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-15229
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Local/Caching
>            Reporter: Benedict
>            Priority: Normal
>
> The BufferPool was never intended to be used for a {{ChunkCache}}, and we 
> need to either change our behaviour to handle uncorrelated lifetimes or use 
> something else.  This is particularly important with the default chunk size 
> for compressed sstables being reduced.  If we address the problem, we should 
> also utilise the BufferPool for native transport connections like we do for 
> internode messaging, and reduce the number of pooling solutions we employ.
> Probably the best thing to do is to improve BufferPool’s behaviour when used 
> for things with uncorrelated lifetimes, which essentially boils down to 
> tracking those chunks that have not been freed and re-circulating them when 
> we run out of completely free blocks.  We should probably also permit 
> instantiating separate {{BufferPool}}, so that we can insulate internode 
> messaging from the {{ChunkCache}}, or at least have separate memory bounds 
> for each, and only share fully-freed chunks.
> With these improvements we can also safely increase the {{BufferPool}} chunk 
> size to 128KiB or 256KiB, to guarantee we can fit compressed pages and reduce 
> the amount of global coordination and per-allocation overhead.  We don’t need 
> 1KiB granularity for allocations, nor 16 byte granularity for tiny 
> allocations.



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