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[2003:cb:c70e:4f00:87ba:e9e9:3821:677b]) by smtp.gmail.com with ESMTPSA id c18-20020adfed92000000b002c54c9bd71fsm15760107wro.93.2023.03.02.06.01.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 02 Mar 2023 06:01:27 -0800 (PST) Message-ID: <982c1623-ac28-2743-d6a3-4faf42f72d47@redhat.com> Date: Thu, 2 Mar 2023 15:01:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH v2] mm/uffd: UFFD_FEATURE_WP_UNPOPULATED To: Peter Xu Cc: Muhammad Usama Anjum , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , Andrew Morton , Mike Rapoport , Axel Rasmussen , Nadav Amit , "kernel@collabora.com" References: <20230227230044.1596744-1-peterx@redhat.com> <640319be-ddb6-d74f-b731-eee5ceab3d01@collabora.com> <8783f47e-76ea-cd24-e373-f2156884cd05@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 2C27C4002B X-Stat-Signature: gecdo5r84cbjioqnorkccfxddoesnxpp X-HE-Tag: 1677765789-63143 X-HE-Meta: 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 7GRn435B wcYlNFgTDcltzUJr5WdfGr2+UdcvPacgNWJ2SaMo9oGXdaBRyNRp5mvWZPBFZnGLdEwF18xPCtMxPVwEoN1iwytahI9CQQ3KqCTjryW7K6WHq19Qurc+RV1wuIbvLLl6R1UQa92+MyenQ94TU4CxFBsfzWtXXj9QzqAaRh5U1JObBYim0c81L8FqAZQyrq+vlHu5pVjZ6LCzp0XhwnhoSVjgb+imbb4Ct4kdoscFaNC8DUtkB9yYdI7TFG+eQ6sxY5pFSZBdAO/kN7i+CsxjrkMDBpK4x8tz1tJvFTfPyQ9yg9yzwY8gUnpSdm5m7a6QvLtE4CVSGIlV4ZQPRZtpaNx5mPyDOZHwTPQObzpLYLwrLD74bC8VY+kbYcjdtM6IbQNwuYLKD4eBX0EGIzP1cLbCVOuJ/AjalXwIFCt/1vfTBfQYhacjH/Xj/rhM4RFM4HxKlBpGtxC43o7rZJLE5l+ds9w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 02.03.23 14:57, Peter Xu wrote: > On Thu, Mar 02, 2023 at 10:37:44AM +0100, David Hildenbrand wrote: >> Especially for such large sparse VMAs, the current way of allocating >> pagetables to place markers/zeropages is far from optimal. > > IMHO that's not a generic workload. As mentioned in the reply there, I > would suggest we go with simple then we have space to optimize it in the > future if necessary, because the API will be the same. > I disagree with "generic workload", we use sparse mmaps all over the place, and when blindly used by e.g., CRIU, we'll simply end up wasting memory and time. But I already agreed that this optimization that is a separate thing to implement. -- Thanks, David / dhildenb