From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: swiotlb detection should be memory hotplug aware ? Date: Fri, 23 Jul 2010 16:33:32 +0200 Message-ID: <4C49A83C.8070203@linux.intel.com> References: <20100721135750Z.fujita.tomonori@lab.ntt.co.jp> <1279732414.10874.6.camel@ank32.eng.vmware.com> <20100722084413I.fujita.tomonori@lab.ntt.co.jp> <20100722090329O.fujita.tomonori@lab.ntt.co.jp> <1279823680.31733.20.camel@ank32.eng.vmware.com> <20100723142208.GA4008@phenom.dumpdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mga11.intel.com ([192.55.52.93]:39214 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752644Ab0GWOdi (ORCPT ); Fri, 23 Jul 2010 10:33:38 -0400 In-Reply-To: <20100723142208.GA4008@phenom.dumpdata.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Konrad Rzeszutek Wilk Cc: Alok Kataria , FUJITA Tomonori , "lenb@kernel.org" , "x86@kernel.org" , "linux-acpi@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Petr Vandrovec > I thought SRAT has NUMA affinity information - so for example my AMD > desktop box has that, but it does not support hotplug capability. > > I think first your 'hotplug_possible' code needs to be more specific - > not just check if SRAT exists, but also if there are swaths of memory > that are non-populated. It would also help if there was some indication > of whether the box truly does a hardware hotplug - is there a way to do > this? The SRAT declares hotplug memory ranges in advance. And Linux already uses this information in the SRAT parser (just the code for doing this is a bit dumb, I have a rewrite somewhere) The only drawback is that some older systems claimed to have large hotplug memory ranges when they didn't actually support it. So it's better to not do anything with a lot of overhead. So yes it would be reasonable to let swiotlb (and possibly other code sizing itself based on memory) call into the SRAT parser and check the hotplug ranges too. BTW longer term swiotlb should be really more dynamic anyways and grow and shrink on demand. I attempted this some time ago with my DMA allocator patchkit, unfortunately that didn't go forward. -Andi