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(p200300cbc708420065d94d0dbb6114c8.dip0.t-ipconnect.de. [2003:cb:c708:4200:65d9:4d0d:bb61:14c8]) by smtp.gmail.com with ESMTPSA id q4-20020adfdfc4000000b002bc6c180738sm5779763wrn.90.2023.01.10.07.47.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Jan 2023 07:47:51 -0800 (PST) Message-ID: <4b52c79e-7b40-1d5e-bd92-d99224be8ba0@redhat.com> Date: Tue, 10 Jan 2023 16:47:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH 00/46] Based on latest mm-unstable (85b44c25cd1e). To: Mike Kravetz Cc: James Houghton , Muchun Song , Peter Xu , David Rientjes , Axel Rasmussen , Mina Almasry , Zach O'Keefe , Manish Mishra , Naoya Horiguchi , "Dr . David Alan Gilbert" , "Matthew Wilcox (Oracle)" , Vlastimil Babka , Baolin Wang , Miaohe Lin , Yang Shi , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230105101844.1893104-1-jthoughton@google.com> <60f06008-dea5-a08e-edec-fc4aec76dfb5@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-Queue-Id: A12E240011 X-Stat-Signature: k1m4yghdc8a7cr1rthguoexo7t5ut4ob X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1673365675-579447 X-HE-Meta: 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 dV7SdRmT yHHKicPlcxOCdOwENxboMJGXWY+kNAxb7t5saEnsqazl0Piwmia1W9mQK/5VTdjceJlcPIlau8XG8sbvymEbNJFo8kYmKifr0RrfJNZmpxACNLmVNb/xzSJx+GFCHAtIh8ELWmWEumrS7DKukzdMUrvM/QA== 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 09.01.23 20:53, Mike Kravetz wrote: > On 01/05/23 11:47, David Hildenbrand wrote: >> On 05.01.23 11:17, James Houghton wrote: >>> This series introduces the concept of HugeTLB high-granularity mapping >>> (HGM). This series teaches HugeTLB how to map HugeTLB pages at >>> high-granularity, similar to how THPs can be PTE-mapped. >>> >>> Support for HGM in this series is for MAP_SHARED VMAs on x86 only. Other >>> architectures and (some) support for MAP_PRIVATE will come later. >> >> Why even care about the complexity of COW-sharable anon pages? TBH, I'd just >> limit this to MAP_SHARED and call it a day. Sure, we can come up with use >> cases for everything (snapshotting VMs using fork while also support >> optimized postcopy), but I think this would need some real justification for >> the added complexity and possible (likely!) issues. > > I believe the primary use case driving this beyond MAP_SHARED would be > poisoning due to memory errors. Extending HGM seems to be the most > elegant way to start providing better support for this. Good point. Although I wonder if in practice, most applicable users either already are, or should switch to, using MAP_SHARED hugetlb. -- Thanks, David / dhildenb