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[2003:cb:c71b:cb00:d372:1da8:9e9e:422d]) by smtp.gmail.com with ESMTPSA id w12-20020a5d608c000000b002c552c6c8c2sm15822655wrt.87.2023.03.08.09.04.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Mar 2023 09:04:23 -0800 (PST) Message-ID: Date: Wed, 8 Mar 2023 18:04:22 +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 v3 1/2] mm/uffd: UFFD_FEATURE_WP_UNPOPULATED To: Peter Xu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muhammad Usama Anjum , Andrea Arcangeli , Axel Rasmussen , Mike Rapoport , Nadav Amit , Paul Gofman , Andrew Morton References: <20230306213925.617814-1-peterx@redhat.com> <20230306213925.617814-2-peterx@redhat.com> <94be7b9f-c33e-c6dc-4132-6cb78f7c0624@redhat.com> <83b3f3ad-19a2-3737-77dd-3c3f9db82194@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-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 228761C0010 X-Stat-Signature: ur8gxqtigidn43wx6e4togqgs9c616y1 X-Rspam-User: X-HE-Tag: 1678295066-908907 X-HE-Meta: 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 cHIFK/gP 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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 08.03.23 17:51, Peter Xu wrote: > On Wed, Mar 08, 2023 at 04:57:55PM +0100, David Hildenbrand wrote: >> Oh, my thinking was that with markers you postpone placing the shared >> zeropage. So the next read access will require a pagefault to map the shared >> zeropage. Your v1 would have performed best in that case I guess. > > Ah, so I misunderstood because the sentence being quote was in another > context I think.. Sorry, I might have messed up the quoting. > > Pagemap may bring overhead constantly though, not sure when vs page faults. > May relevant to num of missing pages. Right, one idea (raised by Dave G. IIRC) was to to the pagemap scanning concurrently from another thread and avoid most of the shared-zeropage dance. -- Thanks, David / dhildenb