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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3475) MapOutputBuffer allocates 4x as much space to record capacity as intended
Date Tue, 03 Jun 2008 01:28:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3475?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12601806#action_12601806
] 

Tsz Wo (Nicholas), SZE commented on HADOOP-3475:
------------------------------------------------

To be consistent, (Integer.SIZE / 8) should be either (Integer.SIZE / Byte.SIZE) or just 4.
Otherwise, patch looks good.

> MapOutputBuffer allocates 4x as much space to record capacity as intended
> -------------------------------------------------------------------------
>
>                 Key: HADOOP-3475
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3475
>             Project: Hadoop Core
>          Issue Type: Bug
>    Affects Versions: 0.17.0
>            Reporter: Chris Douglas
>            Assignee: Chris Douglas
>             Fix For: 0.18.0
>
>         Attachments: 3475-1.patch
>
>
> When setting up its accounting tables, MapTask.MapOutputBuffer calculates the size of
each of its buffers as:
> {noformat}
> Where #total_bytes is $io.sort.mb * 2^20 and #accounting_bytes is $io.sort.record.percent
* #total_bytes
> kvbuffer: #total_bytes - #accounting_bytes
> kvoffsets: 1/4 of #accounting_bytes
> kvindices: 3/4 of #accounting_bytes
> {noformat}
> kvoffsets and kvindices are ints, not bytes; the size of both arrays is incorrectly calculated.

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