From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH part1 v6 4/6] x86/mem-hotplug: Support initialize page tables in bottom-up Date: Wed, 9 Oct 2013 15:47:47 -0400 Message-ID: <20131009194747.GC5592@mtj.dyndns.org> References: <524E2032.4020106@gmail.com> <524E2127.4090904@gmail.com> <5251F9AB.6000203@zytor.com> <525442A4.9060709@gmail.com> <20131009164449.GG22495@htj.dyndns.org> <52558EEF.4050009@gmail.com> <20131009192040.GA5592@mtj.dyndns.org> <5255AEC1.7040500@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <5255AEC1.7040500@intel.com> Sender: owner-linux-mm@kvack.org To: Dave Hansen Cc: Zhang Yanfei , "H. Peter Anvin" , Andrew Morton , "Rafael J . Wysocki" , lenb@kernel.org, Thomas Gleixner , mingo@elte.hu, Toshi Kani , Wanpeng Li , Thomas Renninger , Yinghai Lu , Jiang Liu , Wen Congyang , Lai Jiangshan , isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, Mel Gorman , Minchan Kim , mina86@mina86.com, gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com, lwoodman@redhat.com, Rik van Riel , jweiner@redhat.com, prarit@redhat.com, "x86@kernel.org" , linux-doc@vger.kernel.org, "linux-kernel@vger.kernel.org" List-Id: linux-acpi@vger.kernel.org Hello, On Wed, Oct 09, 2013 at 12:30:09PM -0700, Dave Hansen wrote: > On 10/09/2013 12:20 PM, Tejun Heo wrote: > > Realistically tho, why would people be using 4k mappings on 2T > > machines? > > CONFIG_DEBUG_PAGEALLOC and CONFIG_KMEMCHECK both disable using >4k > pages. I actually ran in to this on a 1TB machine a few weeks ago: > > https://lkml.org/lkml/2013/8/9/546 > > So it's not a common case for stuff that customers have, but it sure as > *HECK* is needed for debugging. But as I said in the same paragraph, parsing SRAT earlier doesn't solve the problem in itself either. Ignoring the option if 4k mapping is required and memory consumption would be prohibitive should work, no? Something like that would be necessary if we're gonna worry about cases like this no matter how we implement it, but, frankly, I'm not sure this is something worth worrying about. Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org