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From "Daniel Dai (JIRA)" <j...@apache.org>
Subject [jira] Updated: (PIG-1443) DefaultTuple underestimate the memory footprint for string
Date Fri, 11 Jun 2010 18:02:13 GMT

     [ https://issues.apache.org/jira/browse/PIG-1443?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Daniel Dai updated PIG-1443:
----------------------------

          Status: Resolved  (was: Patch Available)
    Hadoop Flags: [Reviewed]
      Resolution: Fixed

Patch committed to both trunk and 0.7 branch.

> DefaultTuple underestimate the memory footprint for string
> ----------------------------------------------------------
>
>                 Key: PIG-1443
>                 URL: https://issues.apache.org/jira/browse/PIG-1443
>             Project: Pig
>          Issue Type: Bug
>          Components: impl
>    Affects Versions: 0.7.0
>            Reporter: Daniel Dai
>            Assignee: Daniel Dai
>             Fix For: 0.7.0
>
>         Attachments: PIG-1443-1.patch, PIG-1443-2.patch
>
>
> Currently, in DefaultTuple, we estimate the memory footprint for string as if it is char
array. The formula we use is:  length * 2 + 12. It turns out we underestimate the memory usage
for string. Here is a list of real memory footprint for string we get from memory dump:
> | length of string | memory in bytes |
> | 7 | 56 |
> | 3 | 48 |
> | 1 | 40 |
> I did a search and find the following formula can accurately estimate the memory footprint
for string:
> {code}
> 8 * (int) (((length * 2) + 45) / 8) 
> {code}

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