From owner-freebsd-hackers@FreeBSD.ORG Wed Feb 12 22:07:13 2014 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 150CA958; Wed, 12 Feb 2014 22:07:13 +0000 (UTC) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id DC8F313C9; Wed, 12 Feb 2014 22:07:12 +0000 (UTC) Received: from h2.funkthat.com (localhost [127.0.0.1]) by h2.funkthat.com (8.14.3/8.14.3) with ESMTP id s1CM75kp077533 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 12 Feb 2014 14:07:06 -0800 (PST) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id s1CM75dD077532; Wed, 12 Feb 2014 14:07:05 -0800 (PST) (envelope-from jmg) Date: Wed, 12 Feb 2014 14:07:05 -0800 From: John-Mark Gurney To: "Gumpula, Suresh" Subject: Re: malloc(9) and its alignment Message-ID: <20140212220705.GV34851@funkthat.com> Mail-Followup-To: "Gumpula, Suresh" , Ian Lepore , "freebsd-hackers@freebsd.org" References: <1392214788.1145.52.camel@revolution.hippie.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Wed, 12 Feb 2014 14:07:06 -0800 (PST) Cc: "freebsd-hackers@freebsd.org" , Ian Lepore X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 12 Feb 2014 22:07:13 -0000 Gumpula, Suresh wrote this message on Wed, Feb 12, 2014 at 19:40 +0000: > Thanks Ian for the reply. I will look at the ARM code, but I was thinking why malloc(9) does not return bucket size aligned pointers. Always returning bucket sizes aligned pointers may not be ideal for a cache.. say you have a buffer of 512 bytes, where often only the first 128 bytes are used (but all 512 bytes may be)... If you always align at 512, some cache lines will be more heavily used than others, reducing the effective size of the cache... This is only one reason not aligning to size may be better... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."