Return-Path: X-Original-To: apmail-hadoop-hdfs-issues-archive@minotaur.apache.org Delivered-To: apmail-hadoop-hdfs-issues-archive@minotaur.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id E71FF10752 for ; Sun, 13 Oct 2013 00:29:42 +0000 (UTC) Received: (qmail 54858 invoked by uid 500); 13 Oct 2013 00:29:42 -0000 Delivered-To: apmail-hadoop-hdfs-issues-archive@hadoop.apache.org Received: (qmail 54825 invoked by uid 500); 13 Oct 2013 00:29:42 -0000 Mailing-List: contact hdfs-issues-help@hadoop.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: hdfs-issues@hadoop.apache.org Delivered-To: mailing list hdfs-issues@hadoop.apache.org Received: (qmail 54816 invoked by uid 99); 13 Oct 2013 00:29:42 -0000 Received: from arcas.apache.org (HELO arcas.apache.org) (140.211.11.28) by apache.org (qpsmtpd/0.29) with ESMTP; Sun, 13 Oct 2013 00:29:42 +0000 Date: Sun, 13 Oct 2013 00:29:42 +0000 (UTC) From: "Binglin Chang (JIRA)" To: hdfs-issues@hadoop.apache.org Message-ID: In-Reply-To: References: Subject: [jira] [Commented] (HDFS-5276) FileSystem.Statistics got performance issue on multi-thread read/write. MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-JIRA-FingerPrint: 30527f35849b9dde25b450d4833f0394 [ https://issues.apache.org/jira/browse/HDFS-5276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13793537#comment-13793537 ] Binglin Chang commented on HDFS-5276: ------------------------------------- Hi [~wheat9], volatile cannot be used as atomic variables, its += operation ( incrementAndGet ) is not thread safe, unless you add lock synchronization. > 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, TestFileSystemStatistics.java, 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)