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From "Thejas M Nair (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-1466) Improve log messages for memory usage
Date Fri, 13 Aug 2010 16:16:16 GMT

    [ https://issues.apache.org/jira/browse/PIG-1466?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12898296#action_12898296
] 

Thejas M Nair commented on PIG-1466:
------------------------------------

bq. It would also be nice to know when GC is called but we can make message to reflect that

Olga, Are you suggesting that we should log everytime the memory manager handler is called
or when the memory manager invokes GC after spilling enough memory ?
I am not sure if it is  useful to log every call to the memory manager handler, maybe we can
log the first time for each type of threshold has been exceeded and then every time we actually
spill something to disk.


> Improve log messages for memory usage
> -------------------------------------
>
>                 Key: PIG-1466
>                 URL: https://issues.apache.org/jira/browse/PIG-1466
>             Project: Pig
>          Issue Type: Improvement
>          Components: impl
>    Affects Versions: 0.7.0
>            Reporter: Ashutosh Chauhan
>            Assignee: Thejas M Nair
>            Priority: Minor
>             Fix For: 0.8.0
>
>
> For anything more then a moderately sized dataset Pig usually spits following messages:
> {code}
> 2010-05-27 18:28:31,659 INFO org.apache.pig.impl.util.SpillableMemoryManager: low memory
handler called (Usage
> threshold exceeded) init = 4194304(4096K) used = 672012960(656262K) committed = 954466304(932096K)
max =
> 954466304(932096K)
> 2010-05-27 18:10:52,653 INFO org.apache.pig.impl.util.SpillableMemoryManager: low memory
handler called (Collection
> threshold exceeded) init = 4194304(4096K) used = 954466304(932096K) committed = 954466304(932096K)
max =
> 954466304(932096K)
> {code}
> This seems to confuse users a lot. Once these messages are printed, users tend to believe
that Pig is having hard time with memory, is spilling to disk etc. but in fact Pig might be
cruising along at ease. We should be little more careful what to print in logs. Currently
these are printed when a notification is sent by JVM and some other conditions are met which
may not necessarily indicate low memory condition. Furthermore, with {{InternalCachedBag}}
embraced everywhere in favor of {{DefaultBag}}, these messages have lost their usefulness.
At the every least, we should lower the log level at which these are printed. 

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