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From "Vijay (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-3578) Multithreaded commitlog
Date Mon, 21 Oct 2013 08:32:42 GMT

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

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

    Attachment: ComitlogStress.java

Micro benchmark code attached, try's to update commit log as fast as possible (choose a small
mutation to avoid active segment starvation, we are still creating ~1 CL per second).

It was creating a commit log segment per second, not sure if this is valid comparison to real
world at this time. But the good part it is that it the patch consumes less memory and has
a less swings. 

http://pastebin.com/WeJ0QL8p

> 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, 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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