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Date: Thu, 7 Sep 2017 20:02:00 +0000 (UTC)
From: "Jason Brown (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
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Subject: [jira] [Commented] (CASSANDRA-13789) Reduce memory copies and
 object creations when acting on  ByteBufs
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archived-at: Thu, 07 Sep 2017 20:02:09 -0000


    [ https://issues.apache.org/jira/browse/CASSANDRA-13789?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16157547#comment-16157547 ] 

Jason Brown commented on CASSANDRA-13789:
-----------------------------------------

Pushed a fix here:

||13789-fixes||
|[branch|https://github.com/jasobrown/cassandra/tree/13789-fixes]|
|[dtest|https://builds.apache.org/view/A-D/view/Cassandra/job/Cassandra-devbranch-dtest/291/]|
|[utests|https://circleci.com/gh/jasobrown/cassandra/tree/13789-fixes]|

The problem was in [~norman]'s patch, in both {{CBUtil#writeString}} and {{CBUtil#writeLongString}} he was bumping the writerIndex via {{ByteBuf#writerIndex(int)}}. The problem is that if the new writerIndex value exceeds the capacity of the buffer it throws an {{IndexOutOfBoundsException}}. Previously, we were calling {{ByteBuf#writeShort}} or {{ByteBuf#writeLong}}, which reallocates the buffer if the new writerIndex is larger than the current size.

For now, I've reverted to calling {{ByteBuf#writeShort}} (or {{ByteBuf#writeLong}}), to restore previous behavior (that passes!), and I've added a new {{CBUtilTest}}, as well.

As a further optimization, we can find out why the {{ByteBuf}} is being reallocated to begin with, but that's for another jira.


> Reduce memory copies and object creations when acting on  ByteBufs
> ------------------------------------------------------------------
>
>                 Key: CASSANDRA-13789
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13789
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Norman Maurer
>            Assignee: Norman Maurer
>             Fix For: 4.0
>
>         Attachments: 0001-CBUtil.sizeOfLongString-encodes-String-to-byte-to-ca.patch, 0001-Reduce-memory-copies-and-object-creations-when-actin.patch
>
>
> There are multiple "low-hanging-fruits" when it comes to reduce memory copies and object allocations when acting on ByteBufs.


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