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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12042) Lazy initialize AbstractINodeDiffList#diffs for snapshots to reduce memory consumption
Date Thu, 29 Jun 2017 00:46:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12042?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16067526#comment-16067526
] 

Hadoop QA commented on HDFS-12042:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue}  0m 14s{color} | {color:blue}
Docker mode activated. {color} |
| {color:green}+1{color} | {color:green} @author {color} | {color:green}  0m  0s{color} |
{color:green} The patch does not contain any @author tags. {color} |
| {color:green}+1{color} | {color:green} test4tests {color} | {color:green}  0m  0s{color}
| {color:green} The patch appears to include 1 new or modified test files. {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green} 14m 10s{color}
| {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  0m 57s{color} |
{color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 40s{color}
| {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} mvnsite {color} | {color:green}  1m  1s{color} |
{color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green}  1m 45s{color} |
{color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 42s{color} |
{color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  0m 54s{color}
| {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  0m 51s{color} |
{color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green}  0m 51s{color} | {color:green}
the patch passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 35s{color}
| {color:green} hadoop-hdfs-project/hadoop-hdfs: The patch generated 0 new + 18 unchanged
- 1 fixed = 18 total (was 19) {color} |
| {color:green}+1{color} | {color:green} mvnsite {color} | {color:green}  0m 56s{color} |
{color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} whitespace {color} | {color:green}  0m  0s{color}
| {color:green} The patch has no whitespace issues. {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green}  1m 51s{color} |
{color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 40s{color} |
{color:green} the patch passed {color} |
| {color:red}-1{color} | {color:red} unit {color} | {color:red} 69m 48s{color} | {color:red}
hadoop-hdfs in the patch failed. {color} |
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green}  0m 20s{color}
| {color:green} The patch does not generate ASF License warnings. {color} |
| {color:black}{color} | {color:black} {color} | {color:black} 96m 51s{color} | {color:black}
{color} |
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|| Reason || Tests ||
| Failed junit tests | hadoop.hdfs.server.datanode.TestDataNodeVolumeFailure |
|   | hadoop.hdfs.TestDFSStripedOutputStreamWithFailure080 |
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|| Subsystem || Report/Notes ||
| Docker |  Image:yetus/hadoop:14b5c93 |
| JIRA Issue | HDFS-12042 |
| JIRA Patch URL | https://issues.apache.org/jira/secure/attachment/12874975/HDFS-12042.04.patch
|
| Optional Tests |  asflicense  compile  javac  javadoc  mvninstall  mvnsite  unit  findbugs
 checkstyle  |
| uname | Linux 30ac0dce1acd 3.13.0-116-generic #163-Ubuntu SMP Fri Mar 31 14:13:22 UTC 2017
x86_64 x86_64 x86_64 GNU/Linux |
| Build tool | maven |
| Personality | /testptch/hadoop/patchprocess/precommit/personality/provided.sh |
| git revision | trunk / c1edca1 |
| Default Java | 1.8.0_131 |
| findbugs | v3.1.0-RC1 |
| unit | https://builds.apache.org/job/PreCommit-HDFS-Build/20085/artifact/patchprocess/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt
|
|  Test Results | https://builds.apache.org/job/PreCommit-HDFS-Build/20085/testReport/ |
| modules | C: hadoop-hdfs-project/hadoop-hdfs U: hadoop-hdfs-project/hadoop-hdfs |
| Console output | https://builds.apache.org/job/PreCommit-HDFS-Build/20085/console |
| Powered by | Apache Yetus 0.5.0-SNAPSHOT   http://yetus.apache.org |


This message was automatically generated.



> Lazy initialize AbstractINodeDiffList#diffs for snapshots to reduce memory consumption
> --------------------------------------------------------------------------------------
>
>                 Key: HDFS-12042
>                 URL: https://issues.apache.org/jira/browse/HDFS-12042
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Misha Dmitriev
>            Assignee: Misha Dmitriev
>         Attachments: HDFS-12042.01.patch, HDFS-12042.02.patch, HDFS-12042.03.patch, HDFS-12042.04.patch
>
>
> When snapshot diff operation is performed in a NameNode that manages several million
HDFS files/directories, NN needs a lot of memory. Some of that memory is wasted due to suboptimal
data structures, such as empty or under-populated ArrayLists, etc. Analyzing one heap dump
with jxray (www.jxray.com), we observed the following problems with data structures:
> {code}
> 9. BAD COLLECTIONS
> Total collections: 99,707,902  Bad collections: 88,799,760  Overhead: 9,063,898K (18.2%)
> Top bad collections:
>     Ovhd           Problem     Num objs      Type
> -------------------------------------------------
> 3,056,014K (6.1%)      small     29435572     j.u.ArrayList
> 2,641,373K (5.3%)     1-elem     21837906     j.u.ArrayList
> 864,215K (1.7%)     1-elem      5291813     j.u.TreeSet
> 808,456K (1.6%)     1-elem      3045847     j.u.HashMap
> 602,470K (1.2%)      empty     18549109     j.u.ArrayList
> 441,563K (0.9%)      empty      4356975     j.u.TreeSet
> 373,088K (0.7%)      empty      5297007     j.u.HashMap
> 270,324K (0.5%)      small       931394     j.u.HashMap
> {code}
> The data structures created by HDFS code that suffer from the above problems are, in
particular:
> {code}
>   4,228,182K (8.5%): j.u.ArrayList: 19412263 of small 2,111,087K (4.2%), 12932408 of
1-elem 1,717,585K (3.4%), 12784310 of empty 399,509K (0.8%)
>      <-- org.apache.hadoop.hdfs.server.namenode.snapshot.FileDiffList.diffs <--
org.apache.hadoop.hdfs.server.namenode.snapshot.FileWithSnapshotFeature.diffs <-- org.apache.hadoop.hdfs.server.namenode.INode$Feature[]
<-- org.apache.hadoop.hdfs.server.namenode.INodeFile.features <-- org.apache.hadoop.hdfs.server.blockmanagement.BlockInfo.bc
<-- org.apache.hadoop.util.LightWeightGSet$LinkedElement[] <-- org.apache.hadoop.hdfs.server.blockmanagement.BlocksMap$1.entries
<-- org.apache.hadoop.hdfs.server.blockmanagement.BlocksMap.blocks <-- org.apache.hadoop.hdfs.server.blockmanagement.BlocksMap$1.entries
<-- org.apache.hadoop.hdfs.server.blockmanagement.BlocksMap.blocks <-- org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.blocksMap
<-- org.apache.hadoop.hdfs.server.blockmanagement.BlockManager$BlockReportProcessingThread.this$0
<-- j.l.Thread[] <-- j.l.ThreadGroup.threads <-- j.l.Thread.group <-- Java Static:
org.apache.hadoop.fs.FileSystem$Statistics.STATS_DATA_CLEANER
> {code}
> and
> {code}
>   575,557K (1.2%): j.u.ArrayList: 4363271 of 1-elem 409,056K (0.8%), 2439001 of small
166,482K (0.3%)
>      <-- org.apache.hadoop.hdfs.server.namenode.INodeDirectory.children <-- org.apache.hadoop.util.LightWeightGSet$LinkedElement[]
<-- org.apache.hadoop.util.LightWeightGSet.entries <-- org.apache.hadoop.hdfs.server.namenode.INodeMap.map
<-- org.apache.hadoop.hdfs.server.namenode.FSDirectory.inodeMap <-- org.apache.hadoop.hdfs.server.namenode.FSNamesystem.dir
<-- org.apache.hadoop.hdfs.server.namenode.FSNamesystem$NameNodeResourceMonitor.this$0
<-- org.apache.hadoop.util.Daemon.target <-- org.apache.hadoop.hdfs.server.namenode.FSDirectory.inodeMap
<-- org.apache.hadoop.hdfs.server.namenode.FSNamesystem.dir <-- org.apache.hadoop.hdfs.server.namenode.FSNamesystem$NameNodeResourceMonitor.this$0
<-- org.apache.hadoop.util.Daemon.target <-- j.l.Thread[] <-- j.l.ThreadGroup.threads
<-- j.l.Thread.group <-- Java Static: org.apache.hadoop.fs.FileSystem$Statistics.STATS_DATA_CLEANER
> {code}
> There are several different reference chains that all lead to FileDiffList.diffs or INodeDirectory.children.
The total percentage of memory wasted by these data structures in the analyzed dump is about
12%. By creating these lists lazily and/or with capacity that better matches their actual
size, we should be able to reclaim a significant part of these 12%.



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