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[70.30.145.63]) by smtp.gmail.com with ESMTPSA id d71-20020ae9ef4a000000b0073ba3fd4e4asm10972473qkg.16.2023.03.02.05.57.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Mar 2023 05:57:14 -0800 (PST) Date: Thu, 2 Mar 2023 08:57:13 -0500 From: Peter Xu To: David Hildenbrand 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" Subject: Re: [PATCH v2] mm/uffd: UFFD_FEATURE_WP_UNPOPULATED Message-ID: References: <20230227230044.1596744-1-peterx@redhat.com> <640319be-ddb6-d74f-b731-eee5ceab3d01@collabora.com> <8783f47e-76ea-cd24-e373-f2156884cd05@redhat.com> MIME-Version: 1.0 In-Reply-To: <8783f47e-76ea-cd24-e373-f2156884cd05@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6476B40015 X-Stat-Signature: xxxrt5p81mfu3rrmcwdktuwrfnsjz489 X-HE-Tag: 1677765440-78234 X-HE-Meta: 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 LCZOQMtn 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 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 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. If I want to monitor a super sparse VMA on dirty, one thing I can already try is register with MISSING + WP (!WP_UNPOPULATED). It may be a good intermediate solution to avoid any marker ovearheads. -- Peter Xu