[ https://issues.apache.org/jira/browse/HDFS-9053?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14951674#comment-14951674 ]
Hadoop QA commented on HDFS-9053: --------------------------------- \\ \\ | (x) *{color:red}-1 overall{color}* | \\ \\ || Vote || Subsystem || Runtime || Comment || | {color:red}-1{color} | pre-patch | 17m 35s | Findbugs (version ) appears to be broken on trunk. | | {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 8 new or modified test files. | | {color:green}+1{color} | javac | 7m 55s | There were no new javac warning messages. | | {color:green}+1{color} | javadoc | 10m 33s | There were no new javadoc warning messages. | | {color:red}-1{color} | release audit | 0m 20s | The applied patch generated 1 release audit warnings. | | {color:red}-1{color} | checkstyle | 1m 13s | The applied patch generated 8 new checkstyle issues (total was 0, now 8). | | {color:red}-1{color} | whitespace | 0m 10s | The patch has 1 line(s) that end in whitespace. Use git apply --whitespace=fix. | | {color:green}+1{color} | install | 1m 30s | mvn install still works. | | {color:green}+1{color} | eclipse:eclipse | 0m 35s | The patch built with eclipse:eclipse. | | {color:green}+1{color} | findbugs | 4m 25s | The patch does not introduce any new Findbugs (version 3.0.0) warnings. | | {color:green}+1{color} | common tests | 7m 7s | Tests passed in hadoop-common. | | {color:green}+1{color} | hdfs tests | 190m 7s | Tests passed in hadoop-hdfs. | | | | 241m 41s | | \\ \\ || Subsystem || Report/Notes || | Patch URL | http://issues.apache.org/jira/secure/attachment/12765801/HDFS-9053.006.patch | | Optional Tests | javadoc javac unit findbugs checkstyle | | git revision | trunk / def374e | | Release Audit | https://builds.apache.org/job/PreCommit-HDFS-Build/12911/artifact/patchprocess/patchReleaseAuditProblems.txt | | checkstyle | https://builds.apache.org/job/PreCommit-HDFS-Build/12911/artifact/patchprocess/diffcheckstylehadoop-common.txt | | whitespace | https://builds.apache.org/job/PreCommit-HDFS-Build/12911/artifact/patchprocess/whitespace.txt | | hadoop-common test log | https://builds.apache.org/job/PreCommit-HDFS-Build/12911/artifact/patchprocess/testrun_hadoop-common.txt | | hadoop-hdfs test log | https://builds.apache.org/job/PreCommit-HDFS-Build/12911/artifact/patchprocess/testrun_hadoop-hdfs.txt | | Test Results | https://builds.apache.org/job/PreCommit-HDFS-Build/12911/testReport/ | | Java | 1.7.0_55 | | uname | Linux asf902.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/12911/console | This message was automatically generated. > Support large directories efficiently using B-Tree > -------------------------------------------------- > > Key: HDFS-9053 > URL: https://issues.apache.org/jira/browse/HDFS-9053 > Project: Hadoop HDFS > Issue Type: Improvement > Components: namenode > Reporter: Yi Liu > Assignee: Yi Liu > Priority: Critical > Attachments: HDFS-9053 (BTree with simple benchmark).patch, HDFS-9053 > (BTree).patch, HDFS-9053.001.patch, HDFS-9053.002.patch, HDFS-9053.003.patch, > HDFS-9053.004.patch, HDFS-9053.005.patch, HDFS-9053.006.patch > > > This is a long standing issue, we were trying to improve this in the past. > Currently we use an ArrayList for the children under a directory, and the > children are ordered in the list, for insert/delete, the time complexity is > O\(n), (the search is O(log n), but insertion/deleting causes re-allocations > and copies of arrays), for large directory, the operations are expensive. If > the children grow to 1M size, the ArrayList will resize to > 1M capacity, so > need > 1M * 8bytes = 8M (the reference size is 8 for 64-bits system/JVM) > continuous heap memory, it easily causes full GC in HDFS cluster where > namenode heap memory is already highly used. I recap the 3 main issues: > # Insertion/deletion operations in large directories are expensive because > re-allocations and copies of big arrays. > # Dynamically allocate several MB continuous heap memory which will be > long-lived can easily cause full GC problem. > # Even most children are removed later, but the directory INode still > occupies same size heap memory, since the ArrayList will never shrink. > This JIRA is similar to HDFS-7174 created by [~kihwal], but use B-Tree to > solve the problem suggested by [~shv]. > So the target of this JIRA is to implement a low memory footprint B-Tree and > use it to replace ArrayList. > If the elements size is not large (less than the maximum degree of B-Tree > node), the B-Tree only has one root node which contains an array for the > elements. And if the size grows large enough, it will split automatically, > and if elements are removed, then B-Tree nodes can merge automatically (see > more: https://en.wikipedia.org/wiki/B-tree). It will solve the above 3 > issues. -- This message was sent by Atlassian JIRA (v6.3.4#6332)