From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264265AbUHGTY4 (ORCPT ); Sat, 7 Aug 2004 15:24:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264278AbUHGTY4 (ORCPT ); Sat, 7 Aug 2004 15:24:56 -0400 Received: from shawidc-mo1.cg.shawcable.net ([24.71.223.10]:5847 "EHLO pd3mo1so.prod.shaw.ca") by vger.kernel.org with ESMTP id S264265AbUHGTYx (ORCPT ); Sat, 7 Aug 2004 15:24:53 -0400 Date: Sat, 07 Aug 2004 13:21:11 -0600 From: Robert Hancock Subject: Re: ide-cs using 100% CPU To: linux-kernel Message-id: <006d01c47cb3$b2e133b0$6401a8c0@northbrook> MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 X-Mailer: Microsoft Outlook Express 6.00.2800.1437 Content-type: text/plain; charset=iso-8859-1 Content-transfer-encoding: 7bit X-Priority: 3 X-MSMail-priority: Normal References: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org It isn't that the CPU is doing so much work, it's mostly waiting. However with this type of PIO access, the CPU must do all the reads/writes from the buffer and while doing this the CPU is blocked and cannot do anything else. ----- Original Message ----- From: "Hamie" Newsgroups: fa.linux.kernel To: "Russell King" Cc: Sent: Friday, August 06, 2004 1:46 PM Subject: Re: ide-cs using 100% CPU > 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. > > - > 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/