From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753539AbaH2TQv (ORCPT ); Fri, 29 Aug 2014 15:16:51 -0400 Received: from relay3.sgi.com ([192.48.152.1]:36750 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753104AbaH2TQu (ORCPT ); Fri, 29 Aug 2014 15:16:50 -0400 Message-Id: <20140829191647.364032240@asylum.americas.sgi.com> User-Agent: quilt/0.46-1 Date: Fri, 29 Aug 2014 14:16:47 -0500 From: Mike Travis To: mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com Cc: akpm@linux-foundation.org, msalter@redhat.com, dyoung@redhat.com, riel@redhat.com, peterz@infradead.org, mgorman@suse.de, linux-kernel@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org Subject: [PATCH 0/2] x86: Speed up ioremap operations Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We have a large university system in the UK that is experiencing very long delays modprobing the driver for a specific I/O device. The delay is from 8-10 minutes per device and there are 31 devices in the system. This 4 to 5 hour delay in starting up those I/O devices is very much a burden on the customer. There are two causes for requiring a restart/reload of the drivers. First is periodic preventive maintenance (PM) and the second is if any of the devices experience a fatal error. Both of these trigger this excessively long delay in bringing the system back up to full capability. The problem was tracked down to a very slow IOREMAP operation and the excessively long ioresource lookup to insure that the user is not attempting to ioremap RAM. These patches provide a speed up to that function. --