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Hadoop QA commented on HDFS-8859: --------------------------------- \\ \\ | (x) *{color:red}-1 overall{color}* | \\ \\ || Vote || Subsystem || Runtime || Comment || | {color:blue}0{color} | pre-patch | 19m 2s | Pre-patch trunk compilation is healthy. | | {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 41s | There were no new javac warning messages. | | {color:green}+1{color} | javadoc | 9m 38s | There were no new javadoc warning messages. | | {color:green}+1{color} | release audit | 0m 22s | The applied patch does not increase the total number of release audit warnings. | | {color:red}-1{color} | checkstyle | 1m 46s | The applied patch generated 12 new checkstyle issues (total was 0, now 12). | | {color:red}-1{color} | whitespace | 0m 0s | The patch has 2 line(s) that end in whitespace. Use git apply --whitespace=fix. | | {color:green}+1{color} | install | 1m 29s | mvn install still works. | | {color:green}+1{color} | eclipse:eclipse | 0m 33s | The patch built with eclipse:eclipse. | | {color:green}+1{color} | findbugs | 4m 21s | The patch does not introduce any new Findbugs (version 3.0.0) warnings. | | {color:red}-1{color} | common tests | 22m 17s | Tests failed in hadoop-common. | | {color:red}-1{color} | hdfs tests | 175m 43s | Tests failed in hadoop-hdfs. | | | | 243m 11s | | \\ \\ || Reason || Tests || | Failed unit tests | hadoop.ha.TestZKFailoverController | | | hadoop.net.TestNetUtils | | Timed out tests | org.apache.hadoop.cli.TestHDFSCLI | \\ \\ || Subsystem || Report/Notes || | Patch URL | http://issues.apache.org/jira/secure/attachment/12749402/HDFS-8859.002.patch | | Optional Tests | javadoc javac unit findbugs checkstyle | | git revision | trunk / 8f73bdd | | checkstyle | https://builds.apache.org/job/PreCommit-HDFS-Build/11947/artifact/patchprocess/diffcheckstylehadoop-common.txt | | whitespace | https://builds.apache.org/job/PreCommit-HDFS-Build/11947/artifact/patchprocess/whitespace.txt | | hadoop-common test log | https://builds.apache.org/job/PreCommit-HDFS-Build/11947/artifact/patchprocess/testrun_hadoop-common.txt | | hadoop-hdfs test log | https://builds.apache.org/job/PreCommit-HDFS-Build/11947/artifact/patchprocess/testrun_hadoop-hdfs.txt | | Test Results | https://builds.apache.org/job/PreCommit-HDFS-Build/11947/testReport/ | | Java | 1.7.0_55 | | uname | Linux asf909.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/11947/console | This message was automatically generated. > Improve DataNode (ReplicaMap) memory footprint to save about 45% > ---------------------------------------------------------------- > > Key: HDFS-8859 > URL: https://issues.apache.org/jira/browse/HDFS-8859 > Project: Hadoop HDFS > Issue Type: Improvement > Components: datanode > Reporter: Yi Liu > Assignee: Yi Liu > Priority: Critical > Attachments: HDFS-8859.001.patch, HDFS-8859.002.patch > > > By using following approach we can save about *45%* memory footprint for each > block replica in DataNode memory (This JIRA only talks about *ReplicaMap* in > DataNode), the details are: > In ReplicaMap, > {code} > private final Map<String, Map<Long, ReplicaInfo>> map = > new HashMap<String, Map<Long, ReplicaInfo>>(); > {code} > Currently we use a HashMap {{Map<Long, ReplicaInfo>}} to store the replicas > in memory. The key is block id of the block replica which is already > included in {{ReplicaInfo}}, so this memory can be saved. Also HashMap Entry > has a object overhead. We can implement a lightweight Set which is similar > to {{LightWeightGSet}}, but not a fixed size ({{LightWeightGSet}} uses fix > size for the entries array, usually it's a big value, an example is > {{BlocksMap}}, this can avoid full gc since no need to resize), also we > should be able to get Element through key. > Following is comparison of memory footprint If we implement a lightweight set > as described: > We can save: > {noformat} > SIZE (bytes) ITEM > 20 The Key: Long (12 bytes object overhead + 8 > bytes long) > 12 HashMap Entry object overhead > 4 reference to the key in Entry > 4 reference to the value in Entry > 4 hash in Entry > {noformat} > Total: -44 bytes > We need to add: > {noformat} > SIZE (bytes) ITEM > 4 a reference to next element in ReplicaInfo > {noformat} > Total: +4 bytes > So totally we can save 40bytes for each block replica > And currently one finalized replica needs around 46 bytes (notice: we ignore > memory alignment here). > We can save 1 - (4 + 46) / (44 + 46) = *45%* memory for each block replica > in DataNode. > -- This message was sent by Atlassian JIRA (v6.3.4#6332)