From mboxrd@z Thu Jan 1 00:00:00 1970 Date: 25 Jan 2005 15:49:32 +0100 Date: Tue, 25 Jan 2005 15:49:32 +0100 From: Andi Kleen 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> Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Hellwig , Steve Lord , "Mukker, Atul" , 'Marcelo Tosatti' , 'Mel Gorman' , 'William Lee Irwin III' , 'Linux Memory Management List' , 'Linux Kernel' , 'Grant Grundler' List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org