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From "Rajesh Balamohan (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (PIG-3730) Performance issue in SelfSpillBag
Date Wed, 29 Jan 2014 16:12:10 GMT

     [ https://issues.apache.org/jira/browse/PIG-3730?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Rajesh Balamohan updated PIG-3730:
----------------------------------

    Attachment: PIG-3730-trunk-v1.patch

v1 patch for trunk

> Performance issue in SelfSpillBag
> ---------------------------------
>
>                 Key: PIG-3730
>                 URL: https://issues.apache.org/jira/browse/PIG-3730
>             Project: Pig
>          Issue Type: Bug
>          Components: impl
>    Affects Versions: 0.11
>         Environment: Pig 0.11 with MR-V1
>            Reporter: Rajesh Balamohan
>         Attachments: PIG-3730-trunk-v1.patch
>
>
> We have bunch of joins in our pig scripts (joining 5 to 15 datasets together).  Pig creates
a bunch of REPLICATED, HASH_JOINs and we observed heavy performance degradation in one of
the launched M/R job.  This was specifically on the reducer side.  Taking multiple threaddumps
revealed the following
> "main" prio=10 tid=0x00007fbaa801c000 nid=0x1464 runnable [0x00007fbaaee76000]
>    java.lang.Thread.State: RUNNABLE
> 	at org.apache.hadoop.conf.Configuration.getProps(Configuration.java:1781)
> 	- locked <0x00000000b5316370> (a org.apache.hadoop.mapred.JobConf)
> 	at org.apache.hadoop.conf.Configuration.get(Configuration.java:712)
> 	at org.apache.pig.data.SelfSpillBag$MemoryLimits.init(SelfSpillBag.java:73)
> 	at org.apache.pig.data.SelfSpillBag$MemoryLimits.<init>(SelfSpillBag.java:65)
> 	at org.apache.pig.data.SelfSpillBag.<init>(SelfSpillBag.java:39)
> 	at org.apache.pig.data.InternalCachedBag.<init>(InternalCachedBag.java:63)
> 	at org.apache.pig.data.InternalCachedBag.<init>(InternalCachedBag.java:59)
> 	at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POJoinPackage.getNext(POJoinPackage.java:146)
> 	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapReduce$Reduce.processOnePackageOutput(PigGenericMapReduce.java:422)
> 	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapReduce$Reduce.reduce(PigGenericMapReduce.java:405)
> 	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapReduce$Reduce.reduce(PigGenericMapReduce.java:257)
> 	at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:164)
> 	at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:610)
> 	at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:444)
> 	at org.apache.hadoop.mapred.Child$4.run(Child.java:268)
> 	at java.security.AccessController.doPrivileged(Native Method)
> 	at javax.security.auth.Subject.doAs(Subject.java:415)
> 	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1408)
> 	at org.apache.hadoop.mapred.Child.main(Child.java:262)
> at org.apache.hadoop.conf.Configuration.getProps(Configuration.java:1781)
> 	- locked <0x00000000b5316388> (a org.apache.hadoop.mapred.JobConf)
> 	at org.apache.hadoop.conf.Configuration.get(Configuration.java:712)
> 	at org.apache.pig.data.SelfSpillBag$MemoryLimits.init(SelfSpillBag.java:73)
> 	at org.apache.pig.data.SelfSpillBag$MemoryLimits.<init>(SelfSpillBag.java:65)
> 	at org.apache.pig.data.SelfSpillBag.<init>(SelfSpillBag.java:39)
> 	at org.apache.pig.data.InternalCachedBag.<init>(InternalCachedBag.java:63)
> 	at org.apache.pig.data.InternalCachedBag.<init>(InternalCachedBag.java:59)
> 	at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POJoinPackage.getNext(POJoinPackage.java:146)
> 	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapReduce$Reduce.processOnePackageOutput(PigGenericMapReduce.java:422)
> 	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapReduce$Reduce.reduce(PigGenericMapReduce.java:405)
> 	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapReduce$Reduce.reduce(PigGenericMapReduce.java:257)
> 	at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:164)
> 	at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:610)
> 	at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:444)
> 	at org.apache.hadoop.mapred.Child$4.run(Child.java:268)
> 	at java.security.AccessController.doPrivileged(Native Method)
> 	at javax.security.auth.Subject.doAs(Subject.java:415)
> 	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1408)
> 	at org.apache.hadoop.mapred.Child.main(Child.java:262)
> In certain corner cases (where pig.cachedbag.type is not "default"), InternalCachedBag
is initialized in POJoinPackage.  
> InternalCachedBag internally calls SelfSpillBag--> MemoryLimits --> PigMapReduce.sJobConfInternal.get().get(
>                         PigConfiguration.PROP_CACHEDBAG_MEMUSAGE);
> Since this is happening very frequently, the cost of Configuration.get()  itself is increasing
causing the degradation.  Here is the counters snippet from one of the reducer.
> E.g : counter snippet from a reducer
>         FILE: Number of bytes read 	57,762,717
> 	FILE: Number of bytes written 	25,256,417
>         HDFS: Number of bytes read 	0
> 	HDFS: Number of bytes written 	2,521,311
> 	HDFS: Number of read operations 	0
> 	HDFS: Number of large read operations 	0
> 	HDFS: Number of write operations 	1
>  	Reduce input groups 	4,282,722
> 	Reduce shuffle bytes 	26,858,192
> 	Reduce input records 	4,912,881
> 	Reduce output records 	630,159
> 	Spilled Records 	4,912,881



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