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https://issues.apache.org/jira/browse/CASSANDRA-3411?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Ellis updated CASSANDRA-3411:
--------------------------------------

    Attachment: 3411-cleaned.txt

attaching -cleaned, which is mostly undoing some renaming that obscured the 
real changes here.

I think there's some work to do around the commitlog preallocation:
- Seems like we should try to keep an extra segment ready, so that after we 
exhaust our preallocated quota we don't block for each new segment
- segments to keep around should be our high water mark of active
- if we record that high water mark in the system table, that feels like a 
better way of self-tuning to me than exposing the preallocation count as a 
tuneable
- segment allocation should be done off of the CLExecutor thread.  if we make 
"segments" just "inactive segments" instead of "all segments" then we can make 
it into a blocking queue for that purpose
                
> Pre-allocated, Recycled Commitlog Segment Files
> -----------------------------------------------
>
>                 Key: CASSANDRA-3411
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3411
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Rick Branson
>            Priority: Minor
>         Attachments: 
> 001-pre-allocated-recycled-commitlog-segment-files-CASSANDRA-3411.patch, 
> 3411-cleaned.txt
>
>
> An approach for improving commitlog performance is to pre-allocate the full 
> 128MB segment files and reuse them once all the mutations have been flushed. 
> Pre-allocation allows writes to be performed without modifying the file size 
> metadata, and should (in theory) allow the filesystem to allocate a 
> contiguous block of space for the file. Recycling the segment files prevents 
> the overhead of pre-allocation from impacting overall performance.

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