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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-6890) Remove mmap'ed i/o from read path
Date Fri, 28 Mar 2014 22:04:16 GMT


Jonathan Ellis commented on CASSANDRA-6890:

bq. the option to keep compression off to improve performance seems pretty compelling

You're right, more so than I thought.

bq. Personally, I am -1 on removing mmapped IO as an option until we have an in-process uncompressed
page cache that mitigates these problems.

I think I'd be okay removing it if we can get to within 10%.

> Remove mmap'ed i/o from read path
> ---------------------------------
>                 Key: CASSANDRA-6890
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Joshua McKenzie
>            Assignee: Joshua McKenzie
>            Priority: Minor
>             Fix For: 3.0
>         Attachments: 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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