[
https://issues.apache.org/jira/browse/HDFS-7435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14230068#comment-14230068
]
Daryn Sharp commented on HDFS-7435:
-----------------------------------
Apologies if I wasn't clear. My original patch added a blocksBuffer PB field
with encoding of size : long[]. The demo patch for chunking changes this new
field into a repeating field. The resulting encoding is chunk-size : long[],
chunk-size long[], etc.
I'm fine with chunking, but I don't think the tail should wag the dog. The
in-memory representation of the blocks list is merely an implementation detail
that should not influence the PB encoding. Ie. Leave blocksBuffer as a
non-repeating field, and let the NN chunk the block list however it sees fit.
> PB encoding of block reports is very inefficient
> ------------------------------------------------
>
> Key: HDFS-7435
> URL: https://issues.apache.org/jira/browse/HDFS-7435
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode, namenode
> Affects Versions: 2.0.0-alpha, 3.0.0
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Priority: Critical
> Attachments: HDFS-7435.000.patch, HDFS-7435.001.patch, HDFS-7435.patch
>
>
> Block reports are encoded as a PB repeating long. Repeating fields use an
> {{ArrayList}} with default capacity of 10. A block report containing tens or
> hundreds of thousand of longs (3 for each replica) is extremely expensive
> since the {{ArrayList}} must realloc many times. Also, decoding repeating
> fields will box the primitive longs which must then be unboxed.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
