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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9946) use ioprio_set on compaction threads by default instead of manually throttling
Date Fri, 31 Jul 2015 01:58:05 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14648616#comment-14648616
] 

Ariel Weisberg commented on CASSANDRA-9946:
-------------------------------------------

Setting this is harmless, but the only IO scheduler it works with is CFS unless that has changed
at some point. It also might not do much because the queue for the IO scheduler is small,
but I don't have good experimental data on that other then that you certainly don't get completely
fair IO scheduling.

> use ioprio_set on compaction threads by default instead of manually throttling
> ------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-9946
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9946
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Ariel Weisberg
>             Fix For: 3.x
>
>
> Compaction throttling works as designed, but it has two drawbacks:
> * it requires manual tuning to choose the "right" value for a given machine
> * it does not allow compaction to "burst" above its limit if there is additional i/o
capacity available while there are less application requests to serve
> Using ioprio_set instead solves both of these problems.



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