Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263727AbUC3PcL (ORCPT ); Tue, 30 Mar 2004 10:32:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263721AbUC3PcK (ORCPT ); Tue, 30 Mar 2004 10:32:10 -0500 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:55475 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id S263727AbUC3PbV (ORCPT ); Tue, 30 Mar 2004 10:31:21 -0500 Message-ID: <406992BC.60503@pobox.com> Date: Tue, 30 Mar 2004 10:31:08 -0500 From: Jeff Garzik User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030703 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Marc Bevand CC: Andrew Morton , Linux Kernel Subject: Re: [PATCH] speed up SATA References: <4066021A.20308@pobox.com> <40695FF6.3020401@epita.fr> In-Reply-To: <40695FF6.3020401@epita.fr> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1724 Lines: 59 Marc Bevand wrote: > Jeff Garzik wrote: > >> >> [...] >> With this simple patch, the max request size goes from 128K to 32MB... >> so you can imagine this will definitely help performance. Throughput >> goes up. Interrupts go down. Fun for the whole family. >> [...] > > > I have experienced a noticeable improvement concerning the CPU usage > and disk throughput with this patch. > > Benchmark specs: > > o read from only 1 disk (sda), or from 2 disks (sda+sdb), with > 1 or 2 instances of "dd if=/dev/sd? of=/dev/null bs=100M". > o hardware: two Seagate 160GB SATA, on a Silicon Image 3114, on a > 32-bit/33MHz PCI bus, 1GB RAM. > o software: kernel 2.6.5-rc2-bk6-libata2. [...] Very cool, thanks for benching! > As other people were complaining that the 32MB max request size might be > too > high, I did give a try to 1MB (by replacing "65534" by "2046" in the > patch). > There is no visible differences between 32MB and 1MB. This is not surprising, since: * the scatter-gather table imposes a limit of 8MB * the VM further imposes limits on readahead and writeback So 32MB is the hardware max, but not really achieveable due to other factors. > PS: Jeff: "pci_dma_mapping_error()", in libata-core.c from your latest > 2.6-libata patch, is an unresolved symbol. I have had to comment it out > to be able to compile the kernel. Yeah, this is only found in the bleeding-edge-latest 2.6.x kernels. You did the right thing... Regards, Jeff - 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/