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https://issues.apache.org/jira/browse/HDFS-4461?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Colin Patrick McCabe updated HDFS-4461:
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Description: In the {{DirectoryScanner}}, we create a class {{ScanInfo}}
for every block. This object contains two File objects-- one for the metadata
file, and one for the block file. Since those File objects contain full paths,
users who pick a lengthly path for their volume roots will end up using an
extra N_blocks * path_prefix bytes per block scanned. We also don't really
need to store File objects-- storing strings and then creating File objects as
needed would be cheaper. This would be a nice efficiency improvement. (was:
In the {{DirectoryScanner}}, we create a class {{ScanInfo}} for every block.
This object contains two File objects-- one for the metadata file, and one for
the block file. Since those File objects contain full paths, users who pick a
lengthly path for their volume roots will end up using an extra N_blocks *
path_prefix bytes per block scanned. We also don't really need to store File
objects-- storing strings and then creating File objects as needed would be
cheaper. This has been causing out-of-memory conditions for users who pick
such long volume paths.)
> DirectoryScanner: volume path prefix takes up memory for every block that is
> scanned
> -------------------------------------------------------------------------------------
>
> Key: HDFS-4461
> URL: https://issues.apache.org/jira/browse/HDFS-4461
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.0.3-alpha
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Priority: Minor
> Attachments: HDFS-4461.002.patch, HDFS-4461.003.patch,
> memory-analysis.png
>
>
> In the {{DirectoryScanner}}, we create a class {{ScanInfo}} for every block.
> This object contains two File objects-- one for the metadata file, and one
> for the block file. Since those File objects contain full paths, users who
> pick a lengthly path for their volume roots will end up using an extra
> N_blocks * path_prefix bytes per block scanned. We also don't really need to
> store File objects-- storing strings and then creating File objects as needed
> would be cheaper. This would be a nice efficiency improvement.
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