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Posted to mapreduce-issues@hadoop.apache.org by "Koji Noguchi (JIRA)" <ji...@apache.org> on 2012/08/16 21:09:38 UTC
[jira] [Updated] (MAPREDUCE-4499) Looking for speculative tasks is
very expensive in 1.x
[ https://issues.apache.org/jira/browse/MAPREDUCE-4499?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Koji Noguchi updated MAPREDUCE-4499:
------------------------------------
Attachment: mapreduce-4499-v1.0.2-1.patch
Attaching a patch with if&else rewrite. Trying to change the order of boolean condition but not changing the logic.
> Looking for speculative tasks is very expensive in 1.x
> ------------------------------------------------------
>
> Key: MAPREDUCE-4499
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4499
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: mrv1, performance
> Affects Versions: 1.0.3
> Reporter: Nathan Roberts
> Attachments: mapreduce-4499-v1.0.2-1.patch
>
>
> When there are lots of jobs and tasks active in a cluster, the process of figuring out whether or not to launch a speculative task becomes very expensive.
> I could be missing something but it certainly looks like on every heartbeat we could be scanning 10's of thousands of tasks looking for something which might need to be speculatively executed. In most cases, nothing gets chosen so we completely trashed our data cache and didn't even find a task to schedule, just to do it all over again on the next heartbeat.
> On busy jobtrackers, the following backtrace is very common:
> "IPC Server handler 32 on 50300" daemon prio=10 tid=0x00002ab36c74f800
> nid=0xb50 runnable [0x0000000045adb000]
> java.lang.Thread.State: RUNNABLE
> at java.util.TreeMap.valEquals(TreeMap.java:1182)
> at java.util.TreeMap.containsValue(TreeMap.java:227)
> at java.util.TreeMap$Values.contains(TreeMap.java:940)
> at
> org.apache.hadoop.mapred.TaskInProgress.hasRunOnMachine(TaskInProgress.java:1072)
> at
> org.apache.hadoop.mapred.JobInProgress.findSpeculativeTask(JobInProgress.java:2193)
> - locked <0x00002aaefde82338> (a
> org.apache.hadoop.mapred.JobInProgress)
> at
> org.apache.hadoop.mapred.JobInProgress.findNewMapTask(JobInProgress.java:2417)
> - locked <0x00002aaefde82338> (a
> org.apache.hadoop.mapred.JobInProgress)
> at
> org.apache.hadoop.mapred.JobInProgress.obtainNewNonLocalMapTask(JobInProgress.java:1432)
> - locked <0x00002aaefde82338> (a
> org.apache.hadoop.mapred.JobInProgress)
> at
> org.apache.hadoop.mapred.CapacityTaskScheduler$MapSchedulingMgr.obtainNewTask(CapacityTaskScheduler.java:525)
> at
> org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.getTaskFromQueue(CapacityTaskScheduler.java:322)
> at
> org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.assignTasks(CapacityTaskScheduler.java:419)
> at
> org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.access$500(CapacityTaskScheduler.java:150)
> at
> org.apache.hadoop.mapred.CapacityTaskScheduler.addMapTasks(CapacityTaskScheduler.java:1075)
> at
> org.apache.hadoop.mapred.CapacityTaskScheduler.assignTasks(CapacityTaskScheduler.java:1044)
> - locked <0x00002aab6e27a4c8> (a
> org.apache.hadoop.mapred.CapacityTaskScheduler)
> at org.apache.hadoop.mapred.JobTracker.heartbeat(JobTracker.java:3398)
> - locked <0x00002aab6e191278> (a org.apache.hadoop.mapred.JobTracker)
> ...
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