From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162432AbeCAV52 (ORCPT ); Thu, 1 Mar 2018 16:57:28 -0500 Received: from ale.deltatee.com ([207.54.116.67]:39006 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162136AbeCAV50 (ORCPT ); Thu, 1 Mar 2018 16:57:26 -0500 From: Logan Gunthorpe To: Dan Williams , benh@au1.ibm.com 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> Message-ID: <43ba615f-a6e1-9444-65e1-494169cb415d@deltatee.com> Date: Thu, 1 Mar 2018 14:57:06 -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: <2079ba48-5ae5-5b44-cce1-8175712dd395@deltatee.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, benh@au1.ibm.com, dan.j.williams@intel.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 02:45 PM, Logan Gunthorpe wrote: > It handles it fine for many situations. But when you try to map > something that is at the end of the physical address space then the > spares-vmemmap needs virtual address space that's the size of the > physical address space divided by PAGE_SIZE which may be a little bit > too large... Though, considering this more, maybe this shouldn't be a problem... Lets say you have 56bits of address space. 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.) So I'm not sure what the problem with this is. We still have to ensure all the arches map the memory with the right cache bits but that should be relatively easy to solve. Logan