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AJvYcCUuE5zc5usk/tsCBx6Thgn+/U+oUltckOqep8cqzFdPsoWNRKRZkuK+3dM2lQCqtYXkenL1W+wsEg==@kvack.org X-Gm-Message-State: AOJu0YyixZw7/2PshWbGSaJNCyfcAYWohZwPsCfMQyuOosYlO6JP4jf6 dybrFzltAhE7lBPqLTJ+fr2ZYWVLSD8osg7leawu5NR+yXmC2yxJRgMPFFsrsFXKMNbP1Y1c43k EIYdMCbf8yqLu13Yy5nlrWj5mICfCIbmfzijPF0xYHg== X-Gm-Gg: AY/fxX7+RF2r+BMfTHSdz7QqNPQYrKc/4MryrhhS9qWhsn6S3KELCUUhxnau4vR8VIP IRTYVWFBFokEqRnZXsfLEnHKt7VKZc+tF+0ioITrEtOSK+AWMKESSSDf3XgHvVk5X8+wBXfN2kb CdaiRSvGCCHiUZOCprVbk5KcmgahqHaelAYNa30mYTEexOLTVmoOJ95E5fnY/sgCeqPevZEivu5 KdMkEzCKt4Ns8RFcvqqAw/ycmImNTfb5ZfhxCaVwTv1LO3LAj0UcrAWwrL+YA9cpbsM9JVYy1pc LuhH8nSiC7XzRyIZuSeDWCGcpw== X-Google-Smtp-Source: AGHT+IFeLw7u44MQZgbjsQFGA12sP1qdi+5HsRmBGCX/BEXK6I9KYbtNSPfAQW5/lttSum6QUrCoLo8izwyidq6kWdA= X-Received: by 2002:a17:907:97cf:b0:b7a:72bd:ac65 with SMTP id a640c23a62f3a-b8036ec9e68mr3510206766b.9.1767111529979; Tue, 30 Dec 2025 08:18:49 -0800 (PST) MIME-Version: 1.0 References: <861pkpkffh.fsf@kernel.org> <86jyyecyzh.fsf@kernel.org> <863452cwns.fsf@kernel.org> <864ip99f1a.fsf@kernel.org> In-Reply-To: From: Pasha Tatashin Date: Tue, 30 Dec 2025 11:18:12 -0500 X-Gm-Features: AQt7F2rRyBAWSRSVw8tyvBNQJKwYnaZAfvLVHz2DyBAssxNNcP1N6GpP7-FmoGk Message-ID: Subject: Re: [PATCH] kho: add support for deferred struct page init To: Mike Rapoport Cc: Pratyush Yadav , Evangelos Petrongonas , Alexander Graf , Andrew Morton , Jason Miu , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, nh-open-source@amazon.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 062F82000B X-Stat-Signature: 83pwb8za45oiojnowd84eo13ayw7o6u7 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1767111532-468565 X-HE-Meta: U2FsdGVkX1+GGPrV04VyvukyrLieuG6F8zFn7CYZVfopN7p2Tgbs/rkKa5OC++qJL4QGgon1yNv7cSRR1p16UfJFQBH3xuqZS9fhG9zUvgnJLP/HwN8EnATivBuFNa6QzdFh+8yFHk8kjvObO5Scq4tuI4akND0M0bD8YItprHKLH7RLlK6iVZ9RI0JtzYRIVAlzTAeBHXBF/wAJdnnE+BKpIQAra5wGLmyQ2WFMqMemm7Xsbjwhe3i6ESqeaoIcdDVyv5ghEZxryT7Om6W1IeNzBDy/KHQh6xjk24Z4DHwCe2hXJM/kxkK2RgIctMwxeiGyT5oQUxv53zz44h+8SD+15MMAYSnfPH1kkmNDhVQDf66Rmsm4HoGa0fIJ3HwSzDsYHtLo4+s6C4nWUf0PHXN0izeiR4LMvTx7STTotN/36dd6DOXfqH04ag2LR2vq9s+//YIIjpT55/EcqHwJyPPTZuQ1lOd3f1MAtg5PGCRS3qmbrnoJVDN2pvqch0hdyaHvBZuh4vMBfnFul7Ku0e48VUQKgHGBh4Fx/2M7jzlnIXpY7Zo1ib7z5N0H66WWbdMMMk9LLnNS5y5b89iHFtgHn9j3bcJfJeAuT2i5nDAOijRS2YBaAAmez0hhg41sEKKaaipLLVMjnx/9JlI9jodxpjQGt2f60uMLjUy35TGYDhkknsRIC1kNi4tGQf4hiGWJp6lH2HSTIQQP/w6SWVUPdmLET2NJnnBlv9iIzZpVkvc87YJrQyok+Estmi7CvXgjzrV1RHgYsVpUsSbVQYLtlNb9Q/8lUXfmEtAhHUzA+vhMRO0yIWdulB+vC4p4v70HOfMQGgAqjFXgbi8akau50T+pXRgIAxP8d/FPIwa1lPXT3cwVUg+zIKGdjisNtMrhuQ900BfO9e6Th1fCrCMvTWnzZXQAABRaY3CogwunKlsl0e+JyThlqQGmd543GlbKLlKnHJCDpY9J8wd OikObJfe 9W9tsWXXs9dsDPrN4vdqJ4LnrpxjBKUf926QH5iX+xaeYjajCMH/pl6F/63GiGUdNO82dwj5CVZyoJ+gRw3q8TjSkf2lMoFYXt0PpMRsNX/NAKgNejbMiLO1rfz68+1qPXbR79snBpsZgV/Axx3MSe40ZfXxYvIsWjLoK+Tvj5sPHIXyNVSmtB5Bjm8ZLkPmZRkiPHZfZCbk7tlz/KNLOI3bB1g== 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: On Tue, Dec 30, 2025 at 11:16=E2=80=AFAM Mike Rapoport wr= ote: > > On Tue, Dec 30, 2025 at 11:05:05AM -0500, Pasha Tatashin wrote: > > On Mon, Dec 29, 2025 at 4:03=E2=80=AFPM Pratyush Yadav wrote: > > > > > > The magic is purely sanity checking. It is not used to decide anythin= g > > > other than to make sure this is actually a KHO page. I don't intend t= o > > > change that. My point is, if we make sure the KHO pages are properly > > > initialized during MM init, then restoring can actually be a very che= ap > > > operation, where you only do the sanity checking. You can even put th= e > > > magic check behind CONFIG_KEXEC_HANDOVER_DEBUG if you want, but I thi= nk > > > it is useful enough to keep in production systems too. > > > > It is part of a critical hotpath during blackout, should really be > > behind CONFIG_KEXEC_HANDOVER_DEBUG > > Do you have the numbers? ;-) The fastest reboot we can achieve is ~0.4s on ARM (shutdown+purgatory+boot), let's not add anything to regress, as every microsecond counts during blackout. Pasha