From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 14 Dec 2018 12:29:27 -0800 From: Matthew Wilcox To: Dan Williams Cc: Dave Hansen , John Hubbard , david , =?iso-8859-1?B?Suly9G1l?= Glisse , Jan Kara , John Hubbard , Andrew Morton , Linux MM , tom@talpey.com, Al Viro , benve@cisco.com, Christoph Hellwig , Christopher Lameter , "Dalessandro, Dennis" , Doug Ledford , Jason Gunthorpe , Michal Hocko , Mike Marciniszyn , rcampbell@nvidia.com, Linux Kernel Mailing List , linux-fsdevel Subject: Re: [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions Message-ID: <20181214202927.GI10600@bombadil.infradead.org> References: <20181212215931.GG5037@redhat.com> <20181213005119.GD29416@dastard> <05a68829-6e6d-b766-11b4-99e1ba4bc87b@nvidia.com> <01cf4e0c-b2d6-225a-3ee9-ef0f7e53684d@nvidia.com> <20181214194843.GG10600@bombadil.infradead.org> <20181214200311.GH10600@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: On Fri, Dec 14, 2018 at 12:17:08PM -0800, Dan Williams wrote: > On Fri, Dec 14, 2018 at 12:03 PM Matthew Wilcox wrote: > > Yes; working on the pfn-to-page structure right now as it happens ... > > in the meantime, an XArray for it probably wouldn't be _too_ bad. > > It might... see the recent patch from Ketih responding to complaints > about get_dev_pagemap() lookup overhead: Yeah, I saw. I called xa_dump() on the pgmap_array() running under QEmu and it's truly awful because the NVDIMMs presented by QEmu are very misaligned. If we can make the NVDIMMs better aligned, we won't hit such a bad case in the XArray data structure.