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https://issues.apache.org/jira/browse/HDDS-2301?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rajesh Balamohan updated HDDS-2301:
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Attachment: om_write_profile.png
> Write path: Reducing read contention in rocksDB
> -----------------------------------------------
>
> Key: HDDS-2301
> URL: https://issues.apache.org/jira/browse/HDDS-2301
> Project: Hadoop Distributed Data Store
> Issue Type: Bug
> Affects Versions: 0.5.0
> Reporter: Rajesh Balamohan
> Priority: Major
> Attachments: om_write_profile.png, om_write_profile.png
>
>
> Benchmark:
> ------------
> Simple benchmark which creates 100 and 1000s of keys (empty directory) in OM.
> This is done in a tight loop and multiple threads from client side to add
> enough load on CPU. Note that intention is to understand the bottlenecks in
> OM (intentionally avoiding interactions with SCM & DN).
> Observation:
> -------------
> During write path, Ozone checks {{OMFileRequest.verifyFilesInPath}}. This
> internally calls {{omMetadataManager.getKeyTable().get(dbKeyName)}} for every
> write operation. This turns out to be expensive and chokes the entire read
> path.
> https://github.com/apache/hadoop/blob/trunk/hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/request/file/OMDirectoryCreateRequest.java#L155
> https://github.com/apache/hadoop/blob/trunk/hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/request/file/OMFileRequest.java#L63
> In most of the cases, directory creation would be fresh entry. In such cases,
> it would be good to try with {{RocksDB::keyMayExist}}
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