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From "Koji Noguchi (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-4499) Looking for speculative tasks is very expensive in 1.x
Date Thu, 06 Dec 2012 22:17:10 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-4499?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Koji Noguchi updated MAPREDUCE-4499:
------------------------------------

    Description:     (was: 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)
...)
    
> 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
>            Assignee: Koji Noguchi
>             Fix For: 1.2.0
>
>         Attachments: mapreduce-4499-v1.0.2-1.patch
>
>
>   

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