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Hudson commented on HDFS-5276: ------------------------------ SUCCESS: Integrated in Hadoop-trunk-Commit #4585 (See [https://builds.apache.org/job/Hadoop-trunk-Commit/4585/]) Move HDFS-5276 to 2.3.0 in CHANGES.txt (llu: http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1531228) * /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt HDFS-5276. Remove volatile from LightWeightHashSet. (Junping Du via llu) (llu: http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1531225) * /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt * /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/LightWeightHashSet.java > FileSystem.Statistics got performance issue on multi-thread read/write. > ----------------------------------------------------------------------- > > Key: HDFS-5276 > URL: https://issues.apache.org/jira/browse/HDFS-5276 > Project: Hadoop HDFS > Issue Type: Bug > Affects Versions: 2.0.4-alpha > Reporter: Chengxiang Li > Assignee: Colin Patrick McCabe > Attachments: DisableFSReadWriteBytesStat.patch, HDFS-5276.001.patch, > HDFS-5276.002.patch, HDFSStatisticTest.java, hdfs-test.PNG, jstack-trace.PNG, > ThreadLocalStat.patch > > > FileSystem.Statistics is a singleton variable for each FS scheme, each > read/write on HDFS would lead to a AutomicLong.getAndAdd(). AutomicLong does > not perform well in multi-threads(let's say more than 30 threads). so it may > cause serious performance issue. during our spark test profile, 32 threads > read data from HDFS, about 70% cpu time is spent on > FileSystem.Statistics.incrementBytesRead(). -- This message was sent by Atlassian JIRA (v6.1#6144)