From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268252AbUHFTj5 (ORCPT ); Fri, 6 Aug 2004 15:39:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268257AbUHFTii (ORCPT ); Fri, 6 Aug 2004 15:38:38 -0400 Received: from damned.travellingkiwi.com ([81.6.239.220]:8030 "EHLO ballbreaker.travellingkiwi.com") by vger.kernel.org with ESMTP id S268252AbUHFTeD (ORCPT ); Fri, 6 Aug 2004 15:34:03 -0400 Message-ID: <4113DD20.1010808@travellingkiwi.com> Date: Fri, 06 Aug 2004 20:33:52 +0100 From: Hamie User-Agent: Mozilla Thunderbird 0.7.1 (X11/20040715) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Russell King Cc: linux-kernel@vger.kernel.org Subject: Re: ide-cs using 100% CPU References: <40FA4328.4060304@travellingkiwi.com> <20040806202747.H13948@flint.arm.linux.org.uk> In-Reply-To: <20040806202747.H13948@flint.arm.linux.org.uk> X-Enigmail-Version: 0.84.1.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Russell King wrote: >On Sun, Jul 18, 2004 at 10:30:16AM +0100, Hamie wrote: > > >>Anyone know why this happens? Something busy waiting? (BUt that should >>show as system cpu right?) or something taking out really long locks? >> >> > >It'll be because IDE is using PIO to access the CF card, which could >have long access times (so reading a block of sectors could take some >time _and_ use CPU.) Obviously, PIO requires the use of the CPU, so >the CPU can't be handed off to some other task while this is occuring. > > > Well... I did consider that. And not to disbelieve you, since you know the kernel way better than I do, But decided I was being silly that a 1.6GHz Pentium-M processor should use 100% CPU moving a couple of MB/second across a CF interface... Is 100% CPU not excessive? IIRC my PIII-750 used to use less CPU doing the same job as quick, or even slightly faster... And should it not use system CPU rather than user CPU? TIA Hamish.