From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [PATCH] speed up SATA Date: Sun, 28 Mar 2004 09:37:45 +1000 Sender: linux-ide-owner@vger.kernel.org Message-ID: <40661049.1050004@yahoo.com.au> References: <4066021A.20308@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp104.mail.sc5.yahoo.com ([66.163.169.223]:35970 "HELO smtp104.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S262103AbUC0Xhw (ORCPT ); Sat, 27 Mar 2004 18:37:52 -0500 In-Reply-To: <4066021A.20308@pobox.com> List-Id: linux-ide@vger.kernel.org To: Jeff Garzik Cc: linux-ide@vger.kernel.org, Linux Kernel , Andrew Morton Jeff Garzik wrote: > > The "lba48" feature in ATA allows for addressing of sectors > 137GB, and > also allows for transfers of up to 64K sector, instead of the > traditional 256 sectors in older ATA. > > libata simply limited all transfers to a 200 sectors (just under the 256 > sector limit). This was mainly being careful, and making sure I had a > solution that worked everywhere. I also wanted to see how the iommu S/G > stuff would shake out. > > Things seem to be looking pretty good, so it's now time to turn on > lba48-sized transfers. Most SATA disks will be lba48 anyway, even the > ones smaller than 137GB, for this and other reasons. > > 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. > Hi Jeff, I think 32MB is too much. You incur latency and lose scheduling grainularity. I bet returns start diminishing pretty quickly after 1MB or so.