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https://issues.apache.org/jira/browse/HDFS-2533?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Todd Lipcon updated HDFS-2533:
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Attachment: hdfs-2533.txt
Slightly improved version. I found it was pretty trivial to fix contention in
two other places: in these places we were doing a lock around an file.exists()
call unnecessarily, since we were about to open the file for read right
afterwards. Given that, the exists check is unnecessary - we'll get
FileNotFoundException when we try to read the file.
With this patch the numbers improve to:
| Threads | Trunk | HDFS-2533v2 |
| 4 | 226556 KB/s | 237805 KB/sec (1.05x) |
| 16 | 377474 KB/s | 499399 KB/sec (1.32x) |
| 8 | 410114 KB/s | 474560 KB/sec (1.15x) |
> Remove needless synchronization on FSDataSet.getBlockFile
> ---------------------------------------------------------
>
> Key: HDFS-2533
> URL: https://issues.apache.org/jira/browse/HDFS-2533
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: data-node
> Affects Versions: 0.23.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Priority: Minor
> Attachments: hdfs-2533.txt, hdfs-2533.txt
>
>
> HDFS-1148 discusses lock contention issues in FSDataset. It provides a more
> comprehensive fix, converting it all to RWLocks, etc. This JIRA is for one
> very specific fix which gives a decent performance improvement for
> TestParallelRead: getBlockFile() currently holds the lock which is completely
> unnecessary.
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