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From "Misha Dmitriev (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-7320) Duplicate LiteralByteStrings in SystemCredentialsForAppsProto.credentialsForApp_
Date Fri, 13 Oct 2017 18:08:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-7320?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16203955#comment-16203955
] 

Misha Dmitriev commented on YARN-7320:
--------------------------------------

Checkstyle is a little unhappy, but in the line in question I followed the same pattern that
is used in other places in this file when calling methods on a Builder object, e.g.

{code}
new Builder().
  foo().
  bar().
  baz();
{code}

and not

{code}
new Builder().
  foo().
    bar().
      baz();
{code}

> Duplicate LiteralByteStrings in SystemCredentialsForAppsProto.credentialsForApp_
> --------------------------------------------------------------------------------
>
>                 Key: YARN-7320
>                 URL: https://issues.apache.org/jira/browse/YARN-7320
>             Project: Hadoop YARN
>          Issue Type: Improvement
>            Reporter: Misha Dmitriev
>            Assignee: Misha Dmitriev
>         Attachments: YARN-7320.01.patch, YARN-7320.02.patch
>
>
> Using jxray (www.jxray.com) I've analyzed several heap dumps from YARN Resource Manager
running in a big cluster. The tool uncovered several sources of memory waste. One problem,
which results in wasting more than a quarter of all memory, is a large number of duplicate
{{LiteralByteString}} objects coming from the following reference chain:
> {code}
> 1,011,810K (26.9%): byte[]: 5416705 / 100% dup arrays (22108 unique)
> ↖com.google.protobuf.LiteralByteString.bytes
> ↖org.apache.hadoop.yarn.proto.YarnServerCommonServiceProtos$.credentialsForApp_
> ↖{j.u.ArrayList}
> ↖j.u.Collections$UnmodifiableRandomAccessList.c
> ↖org.apache.hadoop.yarn.proto.YarnServerCommonServiceProtos$NodeHeartbeatResponseProto.systemCredentialsForApps_
> ↖org.apache.hadoop.yarn.server.api.protocolrecords.impl.pb.NodeHeartbeatResponsePBImpl.proto
> ↖org.apache.hadoop.yarn.server.resourcemanager.rmnode.RMNodeImpl.latestNodeHeartBeatResponse
> ↖org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.FSSchedulerNode.rmNode
> ...
> {code}
> That is, collectively reference chains that look as above hold in memory 5.4 million
{{LiteralByteString}} objects, but only ~22 thousand of these objects are unique. Deduplicating
these objects, e.g. using a Google Object Interner instance, would save ~1GB of memory.
> It looks like the main place where the above {{LiteralByteString}}s are created and attached
to the {{SystemCredentialsForAppsProto}} objects is in {{NodeHeartbeatResponsePBImpl.java}},
method {{addSystemCredentialsToProto()}}. Probably adding a call to an interner there will
fix the problem. wi 



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