From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vojtech Pavlik Subject: Re: Compact Flash PIO 4 tuning Date: Tue, 6 May 2003 07:47:34 +0200 Sender: linux-ide-owner@vger.kernel.org Message-ID: <20030506074734.C2287@ucw.cz> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from twilight.ucw.cz ([81.30.235.3]:8663 "EHLO twilight.ucw.cz") by vger.kernel.org with ESMTP id S262376AbTEFFfJ (ORCPT ); Tue, 6 May 2003 01:35:09 -0400 Content-Disposition: inline In-Reply-To: ; from dave-gnus@bfnet.com on Mon, May 05, 2003 at 05:53:35PM -0700 List-Id: linux-ide@vger.kernel.org To: David Wuertele Cc: linux-ide@vger.kernel.org On Mon, May 05, 2003 at 05:53:35PM -0700, David Wuertele wrote: > Howdy, > > I'm working on an embedded system that has a CF card on the IDE bus. > The CF spec only allows PIO mode, and my card can do PIO 4. However, > when I try to stream data from this card into memory at 2 MBytes per > second, it pegs the CPU at 100%. This is ruining the performance of > my application, which has to process this data in real time. > > I realize that PIO 4 requires CPU involvement, but are there ways I > can tune the kernel for copying large files to memory, so that my > application doesn't get starved of CPU? If you use the full bandwidth of the PIO device, you use 100% CPU. That's it and there's no way around. You can check that the IDE/CF interface is set to PIO4 and that under Linux you have IRQ unmasking enabled, those two will help, though the first statement is still valid. -- Vojtech Pavlik SuSE Labs, SuSE CR