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From "Vijay (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-3578) Multithreaded commitlog
Date Mon, 21 Oct 2013 18:02:50 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-3578?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vijay updated CASSANDRA-3578:
-----------------------------

    Attachment: Multi-Threded-CL.png
                Current-CL.png

Hi Jonathan, Ohhh you can ignore those.... i was experimenting few other things (like UUID.random
was locking and the numbers where all bad, etc) and hence added those metrics (didn't mean
to confuse). But if you are interested with the GC profile please see the attached.

> Multithreaded commitlog
> -----------------------
>
>                 Key: CASSANDRA-3578
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3578
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jonathan Ellis
>            Assignee: Vijay
>            Priority: Minor
>              Labels: performance
>         Attachments: 0001-CASSANDRA-3578.patch, ComitlogStress.java, Current-CL.png,
Multi-Threded-CL.png, parallel_commit_log_2.patch
>
>
> Brian Aker pointed out a while ago that allowing multiple threads to modify the commitlog
simultaneously (reserving space for each with a CAS first, the way we do in the SlabAllocator.Region.allocate)
can improve performance, since you're not bottlenecking on a single thread to do all the copying
and CRC computation.
> Now that we use mmap'd CommitLog segments (CASSANDRA-3411) this becomes doable.
> (moved from CASSANDRA-622, which was getting a bit muddled.)



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