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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14466) Enable Direct I/O
Date Sat, 02 Jun 2018 15:17:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14466?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16499100#comment-16499100
] 

Ariel Weisberg commented on CASSANDRA-14466:
--------------------------------------------

Can we try something slightly different? What happens if you run without O_DIRECT, but with
read ahead set to 0 and the compressed chunk length set to 4kb, 8kb, and 16kb?

I think to really pass judgement on adding this feature we would need to do a more apples
to apples comparison.

Can you also provide the exact cassandra-stress invocation you used? Was it using a uniform
distribution or a cacheable distribution?

> Enable Direct I/O 
> ------------------
>
>                 Key: CASSANDRA-14466
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14466
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Local Write-Read Paths
>            Reporter: Mulugeta Mammo
>            Priority: Major
>         Attachments: direct_io.patch
>
>
> Hi,
> JDK 10 introduced a new API for Direct IO that enables applications to bypass the file
system cache and potentially improve performance. Details of this feature can be found at
[https://bugs.openjdk.java.net/browse/JDK-8164900].
> This patch uses the JDK 10 API to enable Direct IO for the Cassandra read path. By default,
we have disabled this feature; but it can be enabled using a  new configuration parameter,
enable_direct_io_for_read_path. We have conducted a Cassandra read-only stress test and measured
a throughput gain of up to 60% on flash drives.
> The patch requires JDK 10 Cassandra Support - https://issues.apache.org/jira/browse/CASSANDRA-9608 
> Please review the patch and let us know your feedback.
> Thanks,
> [^direct_io.patch]
>  



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