From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wproxy.gmail.com (wproxy.gmail.com [64.233.184.200]) by ozlabs.org (Postfix) with ESMTP id A230B679EB for ; Sat, 21 May 2005 04:12:56 +1000 (EST) Received: by wproxy.gmail.com with SMTP id 37so986014wra for ; Fri, 20 May 2005 11:12:54 -0700 (PDT) Message-ID: Date: Fri, 20 May 2005 11:12:54 -0700 From: Shawn Jin To: ppcembed In-Reply-To: <20050519020953.GB11587@gate.ebshome.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 References: <20050519012404.GA11587@gate.ebshome.net> <20050519020953.GB11587@gate.ebshome.net> Subject: Re: DMA consistent allocation is limited to 2MB on 2.6.11 for ppc440? Reply-To: Shawn Jin List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , > My recommendation - don't do this. Why do you need to allocate this > big chunk of consistent memory in the first place? You can do DMA > _without_ allocating "consistent" memory. In fact, this is how > virtually all devices work in Linux. For more info about DMA API - > look at Documentation/DMA-API.txt. The driver stack we've been developing (already 4.0) uses consistent memory a lot for DMA. The stack is for many kinds of high performance storage IO e.g. iSCSI, FC. It works fine on 2.4.x because there is no such 2MB consistent pool limitation. > Technically, you can make consistent pool bigger, if you really insist > on using this approach. I want to understand the motivation and the rationale of choosing 'consistent_pte' on 2.6.x, what impact there would be to increase the consistent pool, and so on. Some pointers to articles, posts are more helpful. Thanks a lot, -Shawn.