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AJvYcCVWkb/8UlHbBHdrOAvWKOrTnMD21YoJ7qxUn8BkPQrbmrS3s83Kq6gevmlwVz+pwsG3rA8e/ZPWbA==@kvack.org X-Gm-Message-State: AOJu0YwvLgOMtY58BUiK7dW1maBkgQq7PmofZCQMNeKr0Aea/zPleRyG bBeFuRH/xixp72a+YdluGvFiT3fmNLKdDbpKl+m+E9T1B7+e6xaNK0EgK2sCVhhVQHRtbVGn0ij bSksxN2JyHbRILP2CvhJBYWF1Qm7FGFI1EYuLHt6OqCvEKog+GLsTInE= X-Gm-Gg: ASbGnctvj/IPOTorEfSIj91VHz8+1J3whqVb0FTZfXerar+PKAuRNp3xyI7Hi/tHV9y SqWjtrNQaa6K0FX7/1Zoz5inwZXgd4bSPTjoxyUA5rwj40v4hs9qnvD8DiIF0Jj7mEENDBFyZCt 8hqXq6bBVnr3bH85qkTHyWFRkprRUtqPXYM//PUZiKPI7DQS3qaaY= X-Google-Smtp-Source: AGHT+IHSkj9Ox3qM4oxVyr5va+0+HoSbN/LLwfuLeFvYTxchuXt69sOnDinqF5sKYnwKgdPq/ii5HJ6fe9Jm7X41Znc= X-Received: by 2002:a05:622a:579a:b0:4a4:3be3:6d69 with SMTP id d75a77b69052e-4a714c8d948mr10914881cf.41.1749594855242; Tue, 10 Jun 2025 15:34:15 -0700 (PDT) MIME-Version: 1.0 References: <20250605171143.76963-1-pratyush@kernel.org> In-Reply-To: From: Pasha Tatashin Date: Tue, 10 Jun 2025 18:33:38 -0400 X-Gm-Features: AX0GCFtJcS6mAcxYKHzkPfp4Zf1aggcovv204XYP6gR6eeACW9WTRiEaZ4dYXr8 Message-ID: Subject: Re: [PATCH] kho: initialize tail pages for higher order folios properly To: Mike Rapoport Cc: Pratyush Yadav , Alexander Graf , Changyuan Lyu , Andrew Morton , Baoquan He , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Clapinski Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 290D48000B X-Stat-Signature: xkuxq6stkihqsoymp5hqzks7fdig6zoq X-Rspam-User: X-HE-Tag: 1749594855-598827 X-HE-Meta: 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 5+7VTdJV 4j/AevU1ZcxTCYOQ4imxZJvmXdNbrmoO9J65oddFre4zNVrj4IMybnBVjzA2Tu+JbTUq8uiyMkTONBUXoRe4GleWKB2elOnbc3kBE5ucVjYHzb+aJOLhL4DNV3p3rhM/YCYpHrM/IELuNKeOSzB84YSvSJHTlU56EEv8NUmB7oh306/VApuhiaYIrWOQ8Ifv1+dPJjj/FBTqIJ5cUtBAVwzzSQpVOzZmU7R7GLycHxgq5C2QehuuydlrknA== 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: List-Subscribe: List-Unsubscribe: > > > I think it should be the other way around, KHO should depend on > > > !DEFERRED_STRUCT_PAGE_INIT. > > > > Agreed, and this is what I first tried, but that does not work, there > > is some circular dependency breaking the build. If you feel > > adventurous you can try that :-) > > Hmm, weird, worked for me :/ I am super confused, it did not work for me over weekend, and now it is working. Even `make menuconfig` would not work. Anyways, I will put it in the appropriate place. > > > > > We will need to teah KHO to work with deferred struct page init. I > > > > suspect, we could init preserved struct pages and then skip over them > > > > during deferred init. > > > > > > We could, but with that would mean we'll run this before SMP and it's not > > > desirable. Also, init_deferred_page() for a random page requires > > > > We already run KHO init before smp_init: > > start_kernel() -> mm_core_init() -> kho_memory_init() -> > > kho_restore_folio() -> struct pages must be already initialized here! > > > > While deferred struct pages are initialized: > > start_kernel() -> rest_init() -> kernel_init() -> > > kernel_init_freeable() -> page_alloc_init_late() -> > > deferred_init_memmap() > > > > If the number of preserved pages that is needed during early boot is > > relatively small, that it should not be an issue to pre-initialize > > struct pages for them before deferred struct pages are initialized. We > > already pre-initialize some "struct pages" that are needed during > > early boot before the reset are initialized, see deferred_grow_zone() > > deferred_grow_zone() takes a chunk in the beginning of uninitialized range, > with kho we are talking about some random pages. If we preinit them early, > deferred_init_memmap() will overwrite them. Yes, this is why I am saying that we would need to skip the KHO initialized "struct pages" somehow during deferred initialization. If we create an ordered by PFN list of early-initialized KHO struct pages, skipping during deferred initialization could be done efficiently. > Anyway, I'm going to look into it, hopefully I'll have something Really > Soon (tm). CC: Michal Clapinski, who was also planning to look into this problem. Pasha