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https://issues.apache.org/jira/browse/HADOOP-1274?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12537926
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acmurthy edited comment on HADOOP-1274 at 10/26/07 4:30 AM:
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Comments:
1. Conversion to short here is unnecessary, probably dangerous:
{noformat}
- metricsRecord.setMetric("taskSlots", (short)maxCurrentTasks);
+ metricsRecord.setMetric("mapTaskSlots", (short)maxCurrentMapTasks);
+ metricsRecord.setMetric("reduceTaskSlots",
+ (short)maxCurrentReduceTasks);
{noformat}
2. Please deprecate {{mapred.tasktracker.tasks.maximum}} for this release, as
per existing norms. We cannot remove it right-away.
{noformat}
- maxCurrentTasks = conf.getInt("mapred.tasktracker.tasks.maximum", 2);
+ maxCurrentMapTasks = conf.getInt(
+ "mapred.tasktracker.map.tasks.maximum", 2);
+ maxCurrentReduceTasks = conf.getInt(
+ "mapred.tasktracker.reduce.tasks.maximum", 1);
{noformat}
{{mapred.tasktracker.tasks.maximum}} should be superceded by
{{mapred.tasktracker.map.tasks.maximum}} and
{{mapred.tasktracker.reduce.tasks.maximum}} for hadoop-0.16.0.
3. Should we consider having different {{JobTracker.PAD_FRACTION}} for maps and
reduces? Clearly the no. of padded slots for reduces should be higher since
reduce-failures are more expensive...
was (Author: acmurthy):
Comments:
1. Conversion to short here is unnecessary, probably dangerous:
{noformat}
- metricsRecord.setMetric("taskSlots", (short)maxCurrentTasks);
+ metricsRecord.setMetric("mapTaskSlots", (short)maxCurrentMapTasks);
+ metricsRecord.setMetric("reduceTaskSlots",
+ (short)maxCurrentReduceTasks);
{noformat}
2. Please deprecate {{mapred.tasktracker.tasks.maximum}} for this release, as
per existing norms. We cannot remove it right-away.
{{mapred.tasktracker.tasks.maximum}} should be superceded by
{{mapred.tasktracker.map.tasks.maximum} and
{{mapred.tasktracker.reduce.tasks.maximum}} for 0.16.0.
{noformat}
- maxCurrentTasks = conf.getInt("mapred.tasktracker.tasks.maximum", 2);
+ maxCurrentMapTasks = conf.getInt(
+ "mapred.tasktracker.map.tasks.maximum", 2);
+ maxCurrentReduceTasks = conf.getInt(
+ "mapred.tasktracker.reduce.tasks.maximum", 1);
{noformat}
3. Should we consider having different {{JobTracker.PAD_FRACTION}} for maps and
reduces? Clearly the no. of padded slots for reduces should be higher since
reduce-failures are more expensive...
> Configuring different number of mappers and reducers per TaskTracker
> --------------------------------------------------------------------
>
> Key: HADOOP-1274
> URL: https://issues.apache.org/jira/browse/HADOOP-1274
> Project: Hadoop
> Issue Type: Improvement
> Components: mapred
> Reporter: Koji Noguchi
> Assignee: Amareshwari Sri Ramadasu
> Priority: Minor
> Fix For: 0.16.0
>
> Attachments: patch-1274.txt
>
>
> Depending on the application, it sometimes make sense to have more mappers
> than reducers assigned to each node.
> (I'm assuming user either has a dedicated cluster or use HOD.)
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