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Posted to issues@tez.apache.org by "Siddharth Seth (JIRA)" <ji...@apache.org> on 2014/10/31 07:34:34 UTC
[jira] [Updated] (TEZ-1522) Scheduling can result in out of order
execution and slowdown of upstream work
[ https://issues.apache.org/jira/browse/TEZ-1522?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Siddharth Seth updated TEZ-1522:
--------------------------------
Attachment: TEZ-1522.1.wip.txt
Patch I was experimenting with earlier today which (temporarily) changes the NaturalOrderDAGScheduler to make scheduling decisions based on when all sources of a vertex have been initialized.
This does solve the problem of scheduling the incorrect vertex (which is waiting for upstream tasks) to some extent (except for VertexSchedulers which throttle their tasks like the ShuffleVertexManager); also ends up ensuing that the source vertices are fully configured - since it will not schedule tasks otherwise.
Got help from [~gopalv] earlier today to try it out on a cluster, and is doing what it's expected to.
> Scheduling can result in out of order execution and slowdown of upstream work
> -----------------------------------------------------------------------------
>
> Key: TEZ-1522
> URL: https://issues.apache.org/jira/browse/TEZ-1522
> Project: Apache Tez
> Issue Type: Bug
> Reporter: Rajesh Balamohan
> Assignee: Rajesh Balamohan
> Priority: Critical
> Labels: performance
> Attachments: TEZ-1522.1.wip.txt, TEZ-1522.am.log.gz, task_runtime.svg
>
>
> M2 M7
> \ /
> (sg) \ /
> R3 / (b)
> \ /
> (b) \ /
> \ /
> M5
> |
> R6
> Plz refer to the attachment (task runtime SVG). In this case, M5 got scheduled much earlier than R3 (green color in the diagram) and retained lots of containers.
> R3 got less containers to work with.
> Attaching the output from the status monitor when the job ran; Map_5 has taken up almost all of cluster resource, whereas Reducer_3 got fraction of the capacity.
> Map_2: 1/1 Map_5: 0(+373)/1000 Map_7: 1/1 Reducer_3: 0/8000 Reducer_6: 0/1
> Map_2: 1/1 Map_5: 0(+374)/1000 Map_7: 1/1 Reducer_3: 0/8000 Reducer_6: 0/1
> Map_2: 1/1 Map_5: 0(+374)/1000 Map_7: 1/1 Reducer_3: 0(+1)/8000 Reducer_6: 0/1
> ....
> Map_2: 1/1 Map_5: 0(+374)/1000 Map_7: 1/1 Reducer_3: 14(+7)/8000 Reducer_6: 0/1
> Map_2: 1/1 Map_5: 0(+374)/1000 Map_7: 1/1 Reducer_3: 63(+14)/8000 Reducer_6: 0/1
> Map_2: 1/1 Map_5: 0(+374)/1000 Map_7: 1/1 Reducer_3: 159(+22)/8000 Reducer_6: 0/1
> Map_2: 1/1 Map_5: 0(+374)/1000 Map_7: 1/1 Reducer_3: 308(+29)/8000 Reducer_6: 0/1
> ...
> Creating this JIRA as a placeholder for scheduler enhancement. One possibililty could be to
> schedule lesser number of tasks in downstream vertices, based on the information available for the upstream vertex.
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