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(p200300cbc7063000cdd38a1094801a33.dip0.t-ipconnect.de. [2003:cb:c706:3000:cdd3:8a10:9480:1a33]) by smtp.gmail.com with ESMTPSA id n16-20020a5d51d0000000b002c56046a3b5sm10666859wrv.53.2023.02.23.08.17.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Feb 2023 08:17:32 -0800 (PST) Message-ID: <0a0b3032-a275-ddc9-697b-a8bc2344d3bc@redhat.com> Date: Thu, 23 Feb 2023 17:17:31 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.2 Subject: Re: [PATCH v2 00/46] hugetlb: introduce HugeTLB high-granularity mapping To: James Houghton Cc: Mina Almasry , Mike Kravetz , Muchun Song , Peter Xu , Andrew Morton , David Rientjes , Axel Rasmussen , Zach O'Keefe , Manish Mishra , Naoya Horiguchi , "Dr . David Alan Gilbert" , "Matthew Wilcox (Oracle)" , Vlastimil Babka , Baolin Wang , Miaohe Lin , Yang Shi , Frank van der Linden , Jiaqi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230218002819.1486479-1-jthoughton@google.com> <28a7208c-939c-19ea-1cf0-298444dffe85@redhat.com> <94a10407-ebcb-7090-ef92-2bbc9416d6fa@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: 84D88A000A X-Stat-Signature: b79tb4e7b81eg7rwro6hfe3au98huzbr X-HE-Tag: 1677169056-375813 X-HE-Meta: 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 osy2hBrw 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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 23.02.23 16:53, James Houghton wrote: > On Thu, Feb 23, 2023 at 1:07 AM David Hildenbrand wrote: >> >> On 22.02.23 21:57, Mina Almasry wrote: >>> On Wed, Feb 22, 2023 at 7:49 AM David Hildenbrand wrote: >>>> >>>> On 21.02.23 22:46, Mike Kravetz wrote: >>>>> On 02/18/23 00:27, 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_64 only. Other >>>>>> architectures and (some) support for MAP_PRIVATE will come later. >>>>>> >>>>>> This series is based on latest mm-unstable (ccd6a73daba9). >>>>>> >>>>>> Notable changes with this series >>>>>> ================================ >>>>>> >>>>>> - hugetlb_add_file_rmap / hugetlb_remove_rmap are added to handle >>>>>> mapcounting for non-anon hugetlb. >>>>>> - The mapcounting scheme uses subpages' mapcounts for high-granularity >>>>>> mappings, but it does not use subpages_mapcount(). This scheme >>>>>> prevents the HugeTLB VMEMMAP optimization from being used, so it >>>>>> will be improved in a later series. >>>>>> - page_add_file_rmap and page_remove_rmap are updated so they can be >>>>>> used by hugetlb_add_file_rmap / hugetlb_remove_rmap. >>>>>> - MADV_SPLIT has been added to enable the userspace API changes that >>>>>> HGM allows for: high-granularity UFFDIO_CONTINUE (and maybe other >>>>>> changes in the future). MADV_SPLIT does NOT force all the mappings to >>>>>> be PAGE_SIZE. >>>>>> - MADV_COLLAPSE is expanded to include HugeTLB mappings. >>>>>> >>>>>> Old versions: >>>>>> v1: https://lore.kernel.org/linux-mm/20230105101844.1893104-1-jthoughton@google.com/ >>>>>> RFC v2: https://lore.kernel.org/linux-mm/20221021163703.3218176-1-jthoughton@google.com/ >>>>>> RFC v1: https://lore.kernel.org/linux-mm/20220624173656.2033256-1-jthoughton@google.com/ >>>>>> >>>>>> Changelog: >>>>>> v1 -> v2 (thanks Peter for all your suggestions!): >>>>>> - Changed mapcount to be more THP-like, and make HGM incompatible with >>>>>> HVO. >>>>>> - HGM is now disabled by default to leave HVO enabled by default. >>>>> >>>>> I understand the reasoning behind the move to THP-like mapcounting, and the >>>>> incompatibility with HVO. However, I just got to patch 5 and realized either >>>>> HGM or HVO will need to be chosen at kernel build time. That may not be an >>>>> issue for cloud providers or others building their own kernels for internal >>>>> use. However, distro kernels will need to pick one option or the other. >>>>> Right now, my Fedora desktop has HVO enabled so it would likely not have >>>>> HGM enabled. That is not a big deal for a desktop. >>>>> >>>>> Just curious, do we have distro kernel users that want to use HGM? >>>> >>>> Most certainly I would say :) > > I'm not sure. Maybe distros want the hwpoison benefits HGM provides? > But that's not implemented in this series. From what I can tell, HGM helps to improve live migration of VMs with gigantic pages. That sounds like a good reason why distros (that support virtualization) might want it independent of hwpoison changes. -- Thanks, David / dhildenb