Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263378AbTIWO71 (ORCPT ); Tue, 23 Sep 2003 10:59:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263381AbTIWO7Z (ORCPT ); Tue, 23 Sep 2003 10:59:25 -0400 Received: from palrel10.hp.com ([156.153.255.245]:40835 "EHLO palrel10.hp.com") by vger.kernel.org with ESMTP id S263378AbTIWO7U (ORCPT ); Tue, 23 Sep 2003 10:59:20 -0400 From: David Mosberger MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16240.24511.375148.520203@napali.hpl.hp.com> Date: Tue, 23 Sep 2003 07:59:11 -0700 To: "David S. Miller" Cc: Peter Chubb , bcrl@kvack.org, ak@suse.de, iod00d@hp.com, peterc@gelato.unsw.edu.au, linux-ns83820@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: NS83820 2.6.0-test5 driver seems unstable on IA64 In-Reply-To: <20030923035118.578203d5.davem@redhat.com> References: <16234.33565.64383.838490@wombat.disy.cse.unsw.edu.au> <20030919043847.GA2996@cup.hp.com> <20030919044315.GC7666@wotan.suse.de> <16234.36238.848366.753588@wombat.chubb.wattle.id.au> <20030919055304.GE16928@wotan.suse.de> <20030919064922.B3783@kvack.org> <16239.38154.969505.748461@wombat.chubb.wattle.id.au> <20030922203629.B21836@kvack.org> <20030922232237.28a5ac4a.davem@redhat.com> <16240.8965.91289.460763@wombat.chubb.wattle.id.au> <20030923035118.578203d5.davem@redhat.com> X-Mailer: VM 7.07 under Emacs 21.2.1 Reply-To: davidm@hpl.hp.com X-URL: http://www.hpl.hp.com/personal/David_Mosberger/ Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1224 Lines: 29 >>>>> On Tue, 23 Sep 2003 03:51:18 -0700, "David S. Miller" said: David> On Tue, 23 Sep 2003 20:40:05 +1000 Peter Chubb David> wrote: >> How expensive is it to take the trap and do a fix up, compared to >> making an aligned copy? As it involves raising and handling a >> fault disassembling the instruction that caused the fault, etc., >> I'd be surprised if it's much less than 1000 cycles, even without >> the printk, although I haven't measured it yet, and can't find >> enough info in the architecture manuals to know what it is. David> A cache miss can cause 100 or so cycles. :) David> And unlike the fixup trap, the printk wakes up a process and David> causes disk activity as syslogd writes to the kernel message David> log file. The printk() is rate-controlled and doesn't happen for every unaligned access. It's average cost can be made as low as we want to, by adjusting the rate. --david - 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/