Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 27 Nov 2001 12:13:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 27 Nov 2001 12:13:24 -0500 Received: from vasquez.zip.com.au ([203.12.97.41]:7442 "EHLO vasquez.zip.com.au") by vger.kernel.org with ESMTP id ; Tue, 27 Nov 2001 12:13:07 -0500 Message-ID: <3C03C96D.B3ACA982@zip.com.au> Date: Tue, 27 Nov 2001 09:12:13 -0800 From: Andrew Morton X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.14-pre8 i686) X-Accept-Language: en MIME-Version: 1.0 To: Ahmed Masud CC: "'lkml'" Subject: Re: Unresponiveness of 2.4.16 In-Reply-To: <000901c17723$b641c990$8604a8c0@googgun.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Ahmed Masud wrote: > > Just to add to the above something I've experienced: > > 2.4.12 - 2.4.14 on a number of AMD Athelon 900 with 256 MB > RAM doing serial I/O would miss data while any DISK writes would > occure. Two possibilities suggest themselves: - Interrupt latency. Last time I checked (a year ago), the worst-case interrupt latency of the IDE drivers was 80 microseconds on a 500MHz PII. That was with `hdparm -u 1'. That's pretty good. Could you please confirm that you're using `hdparm -u 1' against the relevant disk? - The serial port is working OK, but the application which is handling serial IO is blocked on a disk read (something got paged out), and that disk read fails to complete by the time the serial port buffer fills up. I'll send you a patch which makes the VM less inclined to page things out in the presence of heavy writes, and which decreases read latencies. Thanks. - 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/