Return-Path: Delivered-To: apmail-lucene-hadoop-dev-archive@locus.apache.org Received: (qmail 36298 invoked from network); 15 Feb 2006 18:55:34 -0000 Received: from hermes.apache.org (HELO mail.apache.org) (209.237.227.199) by minotaur.apache.org with SMTP; 15 Feb 2006 18:55:34 -0000 Received: (qmail 47042 invoked by uid 500); 15 Feb 2006 18:55:33 -0000 Delivered-To: apmail-lucene-hadoop-dev-archive@lucene.apache.org Received: (qmail 47016 invoked by uid 500); 15 Feb 2006 18:55:33 -0000 Mailing-List: contact hadoop-dev-help@lucene.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: hadoop-dev@lucene.apache.org Delivered-To: mailing list hadoop-dev@lucene.apache.org Received: (qmail 46992 invoked by uid 99); 15 Feb 2006 18:55:33 -0000 X-ASF-Spam-Status: No, hits=0.0 required=10.0 tests= X-Spam-Check-By: apache.org Received: from [192.87.106.226] (HELO ajax.apache.org) (192.87.106.226) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 15 Feb 2006 10:55:30 -0800 Received: from ajax.apache.org (ajax.apache.org [127.0.0.1]) by ajax.apache.org (Postfix) with ESMTP id CB781DE for ; Wed, 15 Feb 2006 19:55:09 +0100 (CET) Message-ID: <155833505.1140029709831.JavaMail.jira@ajax.apache.org> Date: Wed, 15 Feb 2006 19:55:09 +0100 (CET) From: "Doug Cutting (JIRA)" To: hadoop-dev@lucene.apache.org Subject: [jira] Resolved: (HADOOP-38) default splitter should incorporate fs block size In-Reply-To: <1089400937.1139945203207.JavaMail.jira@ajax.apache.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Virus-Checked: Checked by ClamAV on apache.org X-Spam-Rating: minotaur.apache.org 1.6.2 0/1000/N [ http://issues.apache.org/jira/browse/HADOOP-38?page=all ] Doug Cutting resolved HADOOP-38: -------------------------------- Resolution: Fixed I just committed this. > default splitter should incorporate fs block size > ------------------------------------------------- > > Key: HADOOP-38 > URL: http://issues.apache.org/jira/browse/HADOOP-38 > Project: Hadoop > Type: Improvement > Components: mapred > Reporter: Doug Cutting > > By default, the file splitting code should operate as follows. > inputs are *, numMapTasks, minSplitSize, fsBlockSize > output is * > totalSize = sum of all file sizes; > desiredSplitSize = totalSize / numMapTasks; > if (desiredSplitSize > fsBlockSize) /* new */ > desiredSplitSize = fsBlockSize; > if (desiredSplitSize < minSplitSize) > desiredSplitSize = minSplitSize; > chop input files into desiredSplitSize chunks & return them > In other words, the numMapTasks is a desired minimum. We'll try to chop input into at least numMapTasks chunks, each ideally a single fs block. > If there's not enough input data to create numMapTasks tasks, each with an entire block, then we'll permit tasks whose input is smaller than a filesystem block, down to a minimum split size. > This handles cases where: > - each input record takes a lot of time to process. In this case we want to make sure we use all of the cluster. Thus it is important to permit splits smaller than the fs block size. > - input i/o dominates. In this case we want to permit the placement of tasks on hosts where their data is local. This is only possible if splits are fs block size or smaller. > Are there other common cases that this algorithm does not handle well? > The part marked 'new' above is not currently implemented, but I'd like to add it. > Does this sound reasonble? -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira