From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162884AbeCAXUR (ORCPT ); Thu, 1 Mar 2018 18:20:17 -0500 Received: from ale.deltatee.com ([207.54.116.67]:39570 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162811AbeCAXUP (ORCPT ); Thu, 1 Mar 2018 18:20:15 -0500 To: benh@au1.ibm.com, Dan Williams Cc: Jens Axboe , Keith Busch , Oliver OHalloran , Alex Williamson , linux-nvdimm , linux-rdma , linux-pci@vger.kernel.org, Linux Kernel Mailing List , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jason Gunthorpe , Bjorn Helgaas , Max Gurtovoy , Christoph Hellwig References: <20180228234006.21093-1-logang@deltatee.com> <1519876489.4592.3.camel@kernel.crashing.org> <1519876569.4592.4.camel@au1.ibm.com> <1519936477.4592.23.camel@au1.ibm.com> <2079ba48-5ae5-5b44-cce1-8175712dd395@deltatee.com> <43ba615f-a6e1-9444-65e1-494169cb415d@deltatee.com> <1519945204.4592.45.camel@au1.ibm.com> From: Logan Gunthorpe Message-ID: <595acefb-18fc-e650-e172-bae271263c4c@deltatee.com> Date: Thu, 1 Mar 2018 16:19:59 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <1519945204.4592.45.camel@au1.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.162 X-SA-Exim-Rcpt-To: hch@lst.de, maxg@mellanox.com, bhelgaas@google.com, jgg@mellanox.com, jglisse@redhat.com, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-rdma@vger.kernel.org, linux-nvdimm@lists.01.org, alex.williamson@redhat.com, oliveroh@au1.ibm.com, keith.busch@intel.com, axboe@kernel.dk, dan.j.williams@intel.com, benh@au1.ibm.com X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/03/18 04:00 PM, Benjamin Herrenschmidt wrote: > We use only 52 in practice but yes. > >> That's 64PB. If you use need >> a sparse vmemmap for the entire space it will take 16TB which leaves you >> with 63.98PB of address space left. (Similar calculations for other >> numbers of address bits.) > > We only have 52 bits of virtual space for the kernel with the radix > MMU. Ok, assuming you only have 52 bits of physical address space: the sparse vmemmap takes 1TB and you're left with 3.9PB of address space for other things. So, again, why doesn't that work? Is my math wrong? Logan