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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8501) Erasure Coding: Improve memory efficiency of BlockInfoStriped
Date Fri, 28 Aug 2015 15:16:46 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8501?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14719964#comment-14719964
] 

Hadoop QA commented on HDFS-8501:
---------------------------------

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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:red}-1{color} | pre-patch |  15m 39s | Findbugs (version ) appears to be broken on
HDFS-7285. |
| {color:green}+1{color} | @author |   0m  0s | The patch does not contain any @author tags.
|
| {color:green}+1{color} | tests included |   0m  0s | The patch appears to include 1 new
or modified test files. |
| {color:green}+1{color} | javac |   7m 45s | There were no new javac warning messages. |
| {color:green}+1{color} | javadoc |   9m 58s | There were no new javadoc warning messages.
|
| {color:red}-1{color} | release audit |   0m 15s | The applied patch generated 1 release
audit warnings. |
| {color:green}+1{color} | checkstyle |   0m 33s | There were no new checkstyle issues. |
| {color:green}+1{color} | whitespace |   0m  0s | The patch has no lines that end in whitespace.
|
| {color:green}+1{color} | install |   1m 32s | mvn install still works. |
| {color:green}+1{color} | eclipse:eclipse |   0m 33s | The patch built with eclipse:eclipse.
|
| {color:red}-1{color} | findbugs |   2m 41s | The patch appears to introduce 4 new Findbugs
(version 3.0.0) warnings. |
| {color:green}+1{color} | native |   3m  6s | Pre-build of native portion |
| {color:red}-1{color} | hdfs tests | 184m 49s | Tests failed in hadoop-hdfs. |
| | | 226m 55s | |
\\
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|| Reason || Tests ||
| FindBugs | module:hadoop-hdfs |
| Failed unit tests | hadoop.hdfs.TestAppendSnapshotTruncate |
|   | hadoop.hdfs.TestWriteStripedFileWithFailure |
|   | hadoop.hdfs.TestDFSStripedOutputStreamWithFailure |
\\
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|| Subsystem || Report/Notes ||
| Patch URL | http://issues.apache.org/jira/secure/attachment/12752982/HDFS-8501-HDFS-7285.01.patch
|
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | HDFS-7285 / 164cbe6 |
| Release Audit | https://builds.apache.org/job/PreCommit-HDFS-Build/12195/artifact/patchprocess/patchReleaseAuditProblems.txt
|
| Findbugs warnings | https://builds.apache.org/job/PreCommit-HDFS-Build/12195/artifact/patchprocess/newPatchFindbugsWarningshadoop-hdfs.html
|
| hadoop-hdfs test log | https://builds.apache.org/job/PreCommit-HDFS-Build/12195/artifact/patchprocess/testrun_hadoop-hdfs.txt
|
| Test Results | https://builds.apache.org/job/PreCommit-HDFS-Build/12195/testReport/ |
| Java | 1.7.0_55 |
| uname | Linux asf903.gq1.ygridcore.net 3.13.0-36-lowlatency #63-Ubuntu SMP PREEMPT Wed Sep
3 21:56:12 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux |
| Console output | https://builds.apache.org/job/PreCommit-HDFS-Build/12195/console |


This message was automatically generated.

> Erasure Coding: Improve memory efficiency of BlockInfoStriped
> -------------------------------------------------------------
>
>                 Key: HDFS-8501
>                 URL: https://issues.apache.org/jira/browse/HDFS-8501
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Walter Su
>            Assignee: Walter Su
>         Attachments: HDFS-8501-HDFS-7285.01.patch
>
>
> Erasure Coding: Improve memory efficiency of BlockInfoStriped
> Assume we have a BlockInfoStriped:
> {noformat}
> triplets[] = {s0, s1, s2, s3}
> indices[] = {0, 1, 2, 3}
> {noformat}
> {{s0}} means {{storage_0}}
> When we run balancer/mover to re-locate replica on s2, firstly it becomes:
> {noformat}
> triplets[] = {s0, s1, s2, s3, s4}
> indices[] = {0, 1, 2, 3, 2}
> {noformat}
> Then the replica on s2 is removed, finally it becomes:
> {noformat}
> triplets[] = {s0, s1, null, s3, s4}
> indices[] = {0, 1, -1, 3, 2}
> {noformat}
> The worst case is:
> {noformat}
> triplets[] = {null, null, null, null, s4, s5, s6, s7}
> indices[] = {-1, -1, -1, -1, 0, 1, 2, 3}
> {noformat}
> We should learn from {{BlockInfoContiguous.removeStorage(..)}}. When a storage is removed,
we move the last item front.
> With the improvement, the worst case become:
> {noformat}
> triplets[] = {s4, s5, s6, s7, null}
> indices[] = {0, 1, 2, 3, -1}
> {noformat}
> We have an empty slot.
> Notes:
> Assume we copy 4 storage first, then delete 4. Even with the improvement, the worst case
could be:
> {noformat}
> triplets[] = {s4, s5, s6, s7, null, null, null, null}
> indices[] = {0, 1, 2, 3, -1, -1, -1, -1}
> {noformat}
> But the Balancer uses {{delHint}}. So when add one will always delete one. So this case
won't happen for striped and contiguous blocks.
> *idx_i must be moved to slot_i.* So slot_i will have idx_i. So we can do further improvement
in HDFS-8032.



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