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https://issues.apache.org/jira/browse/HADOOP-17408?focusedWorklogId=532169&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-532169
]
ASF GitHub Bot logged work on HADOOP-17408:
-------------------------------------------
Author: ASF GitHub Bot
Created on: 06/Jan/21 22:30
Start Date: 06/Jan/21 22:30
Worklog Time Spent: 10m
Work Description: hadoop-yetus commented on pull request #2514:
URL: https://github.com/apache/hadoop/pull/2514#issuecomment-755756961
:broken_heart: **-1 overall**
| Vote | Subsystem | Runtime | Logfile | Comment |
|:----:|----------:|--------:|:--------:|:-------:|
| +0 :ok: | reexec | 0m 0s | | Docker mode activated. |
| -1 :x: | patch | 0m 9s | |
https://github.com/apache/hadoop/pull/2514 does not apply to trunk. Rebase
required? Wrong Branch? See
https://cwiki.apache.org/confluence/display/HADOOP/How+To+Contribute for help.
|
| Subsystem | Report/Notes |
|----------:|:-------------|
| GITHUB PR | https://github.com/apache/hadoop/pull/2514 |
| Console output |
https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2514/3/console |
| versions | git=2.17.1 |
| Powered by | Apache Yetus 0.13.0-SNAPSHOT https://yetus.apache.org |
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Issue Time Tracking
-------------------
Worklog Id: (was: 532169)
Time Spent: 40m (was: 0.5h)
> Optimize NetworkTopology while sorting of block locations
> ---------------------------------------------------------
>
> Key: HADOOP-17408
> URL: https://issues.apache.org/jira/browse/HADOOP-17408
> Project: Hadoop Common
> Issue Type: Improvement
> Components: common, net
> Reporter: Ahmed Hussein
> Assignee: Ahmed Hussein
> Priority: Major
> Labels: pull-request-available
> Time Spent: 40m
> Remaining Estimate: 0h
>
> In {{NetworkTopology}}, I noticed that there are some hanging fruits to
> improve the performance.
> Inside {{sortByDistance}}, collections.shuffle is performed on the list
> before calling {{secondarySort}}.
> {code:java}
> Collections.shuffle(list, r);
> if (secondarySort != null) {
> secondarySort.accept(list);
> }
> {code}
> However, in different call sites, {{collections.shuffle}} is passed as the
> secondarySort to {{sortByDistance}}. This means that the shuffle is executed
> twice on each list.
> Also, logic wise, it is useless to shuffle before applying a tie breaker
> which might make the shuffle work obsolete.
> In addition, [~daryn] reported that:
> * topology is unnecessarily locking/unlocking to calculate the distance for
> every node
> * shuffling uses a seeded Random, instead of ThreadLocalRandom, which is
> heavily synchronized
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