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https://issues.apache.org/jira/browse/TEZ-776?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14531394#comment-14531394
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Hitesh Shah commented on TEZ-776:
---------------------------------
>From arraylist javadoc:
{code}
Note that this implementation is not synchronized. If multiple threads access
an ArrayList instance concurrently, and at least one of the threads modifies
the list structurally, it must be synchronized externally. (A structural
modification is any operation that adds or deletes one or more elements, or
explicitly resizes the backing array; merely setting the value of an element is
not a structural modification.) This is typically accomplished by synchronizing
on some object that naturally encapsulates the list. If no such object exists,
the list should be "wrapped" using the Collections.synchronizedList method.
This is best done at creation time, to prevent accidental unsynchronized access
to the list:
{code}
> Reduce AM mem usage caused by storing TezEvents
> -----------------------------------------------
>
> Key: TEZ-776
> URL: https://issues.apache.org/jira/browse/TEZ-776
> Project: Apache Tez
> Issue Type: Sub-task
> Reporter: Siddharth Seth
> Assignee: Bikas Saha
> Priority: Blocker
> Attachments: TEZ-776.1.patch, TEZ-776.10.patch, TEZ-776.11.patch,
> TEZ-776.12.patch, TEZ-776.13.patch, TEZ-776.2.patch, TEZ-776.3.patch,
> TEZ-776.4.patch, TEZ-776.5.patch, TEZ-776.6.A.patch, TEZ-776.6.B.patch,
> TEZ-776.7.patch, TEZ-776.8.patch, TEZ-776.9.patch, TEZ-776.ondemand.1.patch,
> TEZ-776.ondemand.2.patch, TEZ-776.ondemand.3.patch, TEZ-776.ondemand.4.patch,
> TEZ-776.ondemand.5.patch, TEZ-776.ondemand.6.patch, TEZ-776.ondemand.7.patch,
> TEZ-776.ondemand.patch, With_Patch_AM_hotspots.png,
> With_Patch_AM_profile.png, Without_patch_AM_CPU_Usage.png,
> events-problem-solutions.txt, with_patch_jmc_output_of_AM.png,
> without_patch_jmc_output_of_AM.png
>
>
> This is open ended at the moment.
> A fair chunk of the AM heap is taken up by TezEvents (specifically
> DataMovementEvents - 64 bytes per event).
> Depending on the connection pattern - this puts limits on the number of tasks
> that can be processed.
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