From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751349AbaH2WbG (ORCPT ); Fri, 29 Aug 2014 18:31:06 -0400 Received: from out1-smtp.messagingengine.com ([66.111.4.25]:50911 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750896AbaH2WbE (ORCPT ); Fri, 29 Aug 2014 18:31:04 -0400 X-Sasl-enc: Ggwvm7Lyx5p4vM8XnJAl5Hbq/KfZMCoPN0B7jxZIvuz4 1409351462 Date: Fri, 29 Aug 2014 15:31:01 -0700 From: Greg KH To: Andrew Morton Cc: Mike Travis , mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com, 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, Alex Thorlton , Cliff Wickman , Russ Anderson Subject: Re: [PATCH 0/2] x86: Speed up ioremap operations Message-ID: <20140829223101.GA13583@kroah.com> References: <20140829195328.511550688@asylum.americas.sgi.com> <20140829131602.72c422ebd2fd3fba426379e8@linux-foundation.org> <5400E62F.8000405@sgi.com> <20140829135200.636dec4a64e2668c2072d787@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140829135200.636dec4a64e2668c2072d787@linux-foundation.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 29, 2014 at 01:52:00PM -0700, Andrew Morton wrote: > On Fri, 29 Aug 2014 13:44:31 -0700 Mike Travis wrote: > > > > > > > On 8/29/2014 1:16 PM, Andrew Morton wrote: > > > On Fri, 29 Aug 2014 14:53:28 -0500 Mike Travis wrote: > > > > > >> > > >> 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. > > >> > > > > > > Really would prefer to have some quantitative testing results in here, > > > as that is the entire point of the patchset. And it leaves the reader > > > wondering "how much of this severe problem remains?". > > > > Okay, I have some results from testing. The modprobe time appears to > > be affected quite a bit by previous activity on the ioresource list, > > which I suspect is due to cache preloading. While the overall > > improvement is impacted by other overhead of starting the devices, > > this drastically improves the modprobe time. > > > > Also our system is considerably smaller so the percentages gained > > will not be the same. Best case improvement with the modprobe > > on our 20 device smallish system was from 'real 5m51.913s' to > > 'real 0m18.275s'. > > Thanks, I slurped that into the changelog. > > > > Also, the -stable backport is a big ask, isn't it? It's arguably > > > notabug and the affected number of machines is small. > > > > > > > Ingo had suggested this. We are definitely pushing it to our distro > > suppliers for our customers. Whether it's a big deal for smaller > > systems is up in the air. Note that the customer system has 31 devices > > on an SSI that includes a large number of other IB and SAS devices > > as well as a number of nodes which all which have discontiguous memory > > segments. I'm envisioning an ioresource list that numbers at least > > several hundred entries. While that's somewhat indicative of typical > > UV systems it is generally not that common otherwise. > > > > So I guess the -stable is merely a suggestion, not a request. > > Cc Greg for his thoughts! Sounds like a good thing for stable. thanks, greg k-h