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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11383) String duplication in org.apache.hadoop.fs.BlockLocation
Date Mon, 15 May 2017 22:13:04 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11383?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16011419#comment-16011419
] 

Hadoop QA commented on HDFS-11383:
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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} 15m 45s{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:red}-1{color} | {color:red} test4tests {color} | {color:red}  0m  0s{color} | {color:red}
The patch doesn't appear to include any new or modified tests. Please justify why no new tests
are needed for this patch. Also please list what manual steps were performed to verify this
patch. {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green} 14m 52s{color}
| {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 14m 31s{color} |
{color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 38s{color}
| {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} mvnsite {color} | {color:green}  1m 13s{color} |
{color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} mvneclipse {color} | {color:green}  0m 21s{color}
| {color:green} trunk passed {color} |
| {color:red}-1{color} | {color:red} findbugs {color} | {color:red}  1m 33s{color} | {color:red}
hadoop-common-project/hadoop-common in trunk has 19 extant Findbugs warnings. {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 53s{color} |
{color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  0m 48s{color}
| {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 15m  0s{color} |
{color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green} 15m  0s{color} | {color:green}
the patch passed {color} |
| {color:orange}-0{color} | {color:orange} checkstyle {color} | {color:orange}  0m 46s{color}
| {color:orange} hadoop-common-project/hadoop-common: The patch generated 4 new + 20 unchanged
- 2 fixed = 24 total (was 22) {color} |
| {color:green}+1{color} | {color:green} mvnsite {color} | {color:green}  1m 12s{color} |
{color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} mvneclipse {color} | {color:green}  0m 22s{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 54s{color} |
{color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 56s{color} |
{color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} unit {color} | {color:green}  8m 23s{color} | {color:green}
hadoop-common in the patch passed. {color} |
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green}  0m 37s{color}
| {color:green} The patch does not generate ASF License warnings. {color} |
| {color:black}{color} | {color:black} {color} | {color:black} 80m 59s{color} | {color:black}
{color} |
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|| Subsystem || Report/Notes ||
| Docker |  Image:yetus/hadoop:14b5c93 |
| JIRA Issue | HDFS-11383 |
| JIRA Patch URL | https://issues.apache.org/jira/secure/attachment/12868138/HDFS-11383.01.patch
|
| Optional Tests |  asflicense  compile  javac  javadoc  mvninstall  mvnsite  unit  findbugs
 checkstyle  |
| uname | Linux 2253381a4ffd 3.13.0-107-generic #154-Ubuntu SMP Tue Dec 20 09:57:27 UTC 2016
x86_64 x86_64 x86_64 GNU/Linux |
| Build tool | maven |
| Personality | /testptch/hadoop/patchprocess/precommit/personality/provided.sh |
| git revision | trunk / c48f297 |
| Default Java | 1.8.0_131 |
| findbugs | v3.1.0-RC1 |
| findbugs | https://builds.apache.org/job/PreCommit-HDFS-Build/19434/artifact/patchprocess/branch-findbugs-hadoop-common-project_hadoop-common-warnings.html
|
| checkstyle | https://builds.apache.org/job/PreCommit-HDFS-Build/19434/artifact/patchprocess/diff-checkstyle-hadoop-common-project_hadoop-common.txt
|
|  Test Results | https://builds.apache.org/job/PreCommit-HDFS-Build/19434/testReport/ |
| modules | C: hadoop-common-project/hadoop-common U: hadoop-common-project/hadoop-common
|
| Console output | https://builds.apache.org/job/PreCommit-HDFS-Build/19434/console |
| Powered by | Apache Yetus 0.5.0-SNAPSHOT   http://yetus.apache.org |


This message was automatically generated.



> String duplication in org.apache.hadoop.fs.BlockLocation
> --------------------------------------------------------
>
>                 Key: HDFS-11383
>                 URL: https://issues.apache.org/jira/browse/HDFS-11383
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Misha Dmitriev
>            Assignee: Misha Dmitriev
>         Attachments: HDFS-11383.01.patch
>
>
> I am working on Hive performance, investigating the problem of high memory pressure when
(a) a table consists of a high number (thousands) of partitions and (b) multiple queries run
against it concurrently. It turns out that a lot of memory is wasted due to data duplication.
One source of duplicate strings is class org.apache.hadoop.fs.BlockLocation. Its fields such
as storageIds, topologyPaths, hosts, names, may collectively use up to 6% of memory in my
benchmark, causing (together with other problematic classes) a huge memory spike. Of these
6% of memory taken by BlockLocation strings, more than 5% are wasted due to duplication.
> I think we need to add calls to String.intern() in the BlockLocation constructor, like:
> {code}
> this.hosts = internStringsInArray(hosts);
> ...
> private void internStringsInArray(String[] sar) {
>   for (int i = 0; i < sar.length; i++) {
>     sar[i] = sar[i].intern();
>   }
> }
> {code}
> String.intern() performs very well starting from JDK 7. I've found some articles explaining
the progress that was made by the HotSpot JVM developers in this area, verified that with
benchmarks myself, and finally added quite a bit of interning to one of the Cloudera products
without any issues.



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