Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 19 Apr 2002 04:33:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 19 Apr 2002 04:33:58 -0400 Received: from lightning.swansea.linux.org.uk ([194.168.151.1]:35852 "EHLO the-village.bc.nu") by vger.kernel.org with ESMTP id ; Fri, 19 Apr 2002 04:33:58 -0400 Subject: Re: Bio pool & scsi scatter gather pool usage To: joe@fib011235813.fsnet.co.uk (Joe Thornber) Date: Fri, 19 Apr 2002 09:51:10 +0100 (BST) Cc: lord@sgi.com (Stephen Lord), akpm@zip.com.au (Andrew Morton), alan@lxorguk.ukuu.org.uk (Alan Cox), peloquin@us.ibm.com (Mark Peloquin), linux-kernel@vger.kernel.org In-Reply-To: <20020419080814.GA1181@fib011235813.fsnet.co.uk> from "Joe Thornber" at Apr 19, 2002 09:08:14 AM X-Mailer: ELM [version 2.5 PL6] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: From: Alan Cox Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > This is exactly the problem; I don't think it's going to be unusual to > see volumes that have a variety of mappings. For example the > 'journal' area of the lv with a single fast pv, 'small file' area with > a linear mapping across normal pv's, and finally a 'large file' area > that has a few slower disks striped together. Optimise for the sane cases. Remember the lvm can chain bio's trivially itself. Its a lot cheaper to chain them than unchain them > The last thing I want in this situation is to split up all the io into > the lowest common chunk size, in this case the striped area which will > typically be < 64k. The last thing I want is layers of bio support garbage slowing down a perfectly sane machine that does not need them... Alan - 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/