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Posted to dev@pig.apache.org by "Daniel Dai (JIRA)" <ji...@apache.org> on 2010/06/09 19:34:14 UTC
[jira] Updated: (PIG-1443) DefaultTuple underestimate the memory
footprint for string
[ https://issues.apache.org/jira/browse/PIG-1443?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Daniel Dai updated PIG-1443:
----------------------------
Attachment: PIG-1443-1.patch
> 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: 0.8.0
>
> Attachments: PIG-1443-1.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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