[jira] [Updated] (CASSANDRA-6890) Standardize on a single read path

["Joshua McKenzie (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-6890?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Joshua McKenzie updated CASSANDRA-6890:
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    Attachment: 6890_v1.txt

v1 attached.  Performance differential on 6890 vs. trunk is comparable.

One thing to keep in mind: SegmentedFile.java won't accept any sstables with DiskAccessMode other than "standard" if we yank the other formats completely, as per v1 here.  We'll need some conversion to take sstables w/serializedBounds as auto / mmap / mmap_index_only into a 3.x system.

> Standardize on a single read path
> ---------------------------------
>
>                 Key: CASSANDRA-6890
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6890
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Joshua McKenzie
>            Assignee: Joshua McKenzie
>              Labels: performance
>             Fix For: 3.0
>
>         Attachments: 6890_v1.txt, mmap_gc.jpg, mmap_jstat.txt, mmap_perf.txt, nommap_gc.jpg, nommap_jstat.txt
>
>
> Since we actively unmap unreferenced SSTR's and also copy data out of those readers on the read path, the current memory mapped i/o is a lot of complexity for very little payoff.  Clean out the mmapp'ed i/o on the read path.



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