Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261964AbVAYOtf (ORCPT ); Tue, 25 Jan 2005 09:49:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261965AbVAYOtf (ORCPT ); Tue, 25 Jan 2005 09:49:35 -0500 Received: from colin2.muc.de ([193.149.48.15]:18962 "HELO colin2.muc.de") by vger.kernel.org with SMTP id S261964AbVAYOtd (ORCPT ); Tue, 25 Jan 2005 09:49:33 -0500 Date: 25 Jan 2005 15:49:32 +0100 Date: Tue, 25 Jan 2005 15:49:32 +0100 From: Andi Kleen To: Christoph Hellwig , Steve Lord , "Mukker, Atul" , "'Marcelo Tosatti'" , "'Mel Gorman'" , "'William Lee Irwin III'" , "'Linux Memory Management List'" , "'Linux Kernel'" , "'Grant Grundler'" Subject: Re: [PATCH] Avoiding fragmentation through different allocator Message-ID: <20050125144932.GA75109@muc.de> References: <0E3FA95632D6D047BA649F95DAB60E5705A70E61@exa-atlanta> <41F65514.3040707@xfs.org> <20050125142757.GA20442@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050125142757.GA20442@infradead.org> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1184 Lines: 26 On Tue, Jan 25, 2005 at 02:27:57PM +0000, Christoph Hellwig wrote: > > It is not the driver per se, but the way the memory which is the I/O > > source/target is presented to the driver. In linux there is a good > > chance it will have to use more scatter gather elements to represent > > the same amount of data. > > Note that a change made a few month ago after seeing issues with > aacraid means it's much more likely to see contingous memory, > there were some numbers on linux-scsi and/or linux-kernel. But only at the beginning. iirc after a few days of uptime and memory fragmentation it degenerates back to the old numbers. Perhaps the recent anti defragmentation work will help more. -Andi P.S.: on a AMD x86-64 box the theory can be relatively easily tested: just run with iommu=force,biomerge that will use the IOMMU to merge SG elements. I just don't recommend it for production because some errors are not well handled. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/