From mapreduce-issues-return-4766-apmail-hadoop-mapreduce-issues-archive=hadoop.apache.org@hadoop.apache.org Sat Oct 10 06:43:57 2009 Return-Path: Delivered-To: apmail-hadoop-mapreduce-issues-archive@minotaur.apache.org Received: (qmail 91027 invoked from network); 10 Oct 2009 06:43:57 -0000 Received: from hermes.apache.org (HELO mail.apache.org) (140.211.11.3) by minotaur.apache.org with SMTP; 10 Oct 2009 06:43:57 -0000 Received: (qmail 9412 invoked by uid 500); 10 Oct 2009 06:43:57 -0000 Delivered-To: apmail-hadoop-mapreduce-issues-archive@hadoop.apache.org Received: (qmail 9355 invoked by uid 500); 10 Oct 2009 06:43:57 -0000 Mailing-List: contact mapreduce-issues-help@hadoop.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: mapreduce-issues@hadoop.apache.org Delivered-To: mailing list mapreduce-issues@hadoop.apache.org Received: (qmail 9344 invoked by uid 99); 10 Oct 2009 06:43:56 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Sat, 10 Oct 2009 06:43:56 +0000 X-ASF-Spam-Status: No, hits=-2000.0 required=10.0 tests=ALL_TRUSTED X-Spam-Check-By: apache.org Received: from [140.211.11.140] (HELO brutus.apache.org) (140.211.11.140) by apache.org (qpsmtpd/0.29) with ESMTP; Sat, 10 Oct 2009 06:43:52 +0000 Received: from brutus (localhost [127.0.0.1]) by brutus.apache.org (Postfix) with ESMTP id 93205234C4AE for ; Fri, 9 Oct 2009 23:43:31 -0700 (PDT) Message-ID: <1468662077.1255157011600.JavaMail.jira@brutus> Date: Fri, 9 Oct 2009 23:43:31 -0700 (PDT) From: "Chris Douglas (JIRA)" To: mapreduce-issues@hadoop.apache.org Subject: [jira] Updated: (MAPREDUCE-64) Map-side sort is hampered by io.sort.record.percent MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-JIRA-FingerPrint: 30527f35849b9dde25b450d4833f0394 X-Virus-Checked: Checked by ClamAV on apache.org [ https://issues.apache.org/jira/browse/MAPREDUCE-64?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Chris Douglas updated MAPREDUCE-64: ----------------------------------- Status: Patch Available (was: Open) > Map-side sort is hampered by io.sort.record.percent > --------------------------------------------------- > > Key: MAPREDUCE-64 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-64 > Project: Hadoop Map/Reduce > Issue Type: Bug > Reporter: Arun C Murthy > Assignee: Chris Douglas > Attachments: M64-0.patch, M64-1.patch > > > Currently io.sort.record.percent is a fairly obscure, per-job configurable, expert-level parameter which controls how much accounting space is available for records in the map-side sort buffer (io.sort.mb). Typically values for io.sort.mb (100) and io.sort.record.percent (0.05) imply that we can store ~350,000 records in the buffer before necessitating a sort/combine/spill. > However for many applications which deal with small records e.g. the world-famous wordcount and it's family this implies we can only use 5-10% of io.sort.mb i.e. (5-10M) before we spill inspite of having _much_ more memory available in the sort-buffer. The word-count for e.g. results in ~12 spills (given hdfs block size of 64M). The presence of a combiner exacerbates the problem by piling serialization/deserialization of records too... > Sure, jobs can configure io.sort.record.percent, but it's tedious and obscure; we really can do better by getting the framework to automagically pick it by using all available memory (upto io.sort.mb) for either the data or accounting. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.