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Tue, 20 Jun 2023 03:36:34 -0700 (PDT) Received: from google.com ([2401:fa00:8f:203:b84a:9c37:6b9:859b]) by smtp.gmail.com with ESMTPSA id c12-20020aa78e0c000000b0063f2a5a59d1sm1073475pfr.190.2023.06.20.03.36.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Jun 2023 03:36:34 -0700 (PDT) Date: Tue, 20 Jun 2023 19:36:29 +0900 From: Sergey Senozhatsky To: Alexey Romanov Cc: minchan@kernel.org, senozhatsky@chromium.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel@sberdevices.ru Subject: Re: [PATCH v1 1/2] zsmalloc: add allocated objects counter for subpage Message-ID: <20230620103629.GA42985@google.com> References: <20230619143506.45253-1-avromanov@sberdevices.ru> <20230619143506.45253-2-avromanov@sberdevices.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230619143506.45253-2-avromanov@sberdevices.ru> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 145074001A X-Stat-Signature: qk9uh4r4xemzoo5aro6sjhep3wr1bizt X-Rspam-User: X-HE-Tag: 1687257395-257842 X-HE-Meta: U2FsdGVkX19V3wCG0UHkFUz7vdqOyjsmByJrCqVwuw0ZeSKlicFs4yC3EGhCp4CLPHaD6adrZh0DsvBddEpQ/3xUnftUPu7C8bpW2VqaJMve8pZWP2HFlqSd+RgQNbzGYnRLXSkqHPswXuMwImvG+MbSImw78q/QWMAeR953oYNcqaX7SF/8jj6qSi1VamsqTb8/I7Snwz8T1Z7RGiH3TUneiVAKnmyLKoHJQV2kFstbKJCmOMmUHenVIsGJWl0d20R4weNhn7mBsfwZwwkWWGCi45AP317cVdQC4CvJOPL1fYl1M+JEpDkCWiuQ8ep8eBcnKpTThOeDMumk7mtOSQLyMLOF6Jp7D8K5hDDgAAHKRL0iCokukaYfU54ItZAjI1EDhDwG0/AGTTxMG3kfGY0Aoq99JDw/IQs6TW2DWumhfP0B2WsAsh7k/1ug+B+hPWvDAwDhzdi0NxkIM70Dlc3kEoHAJg9whsPJrITZr0nNoQ4FlGK85b+0nIX39F8ZGI5E3wWtimpFkySmrzeg83xjztxnj1cTkJ6RlDgGRM7cKQByxGhPILgz/EROXfArSLXmP29+ZPpUPYNUbhDbloTOR3K+eXSxVqLvnkZkwNgn+6kH/iaC/GqU0MBwDRmy230bQWdVRDuOXuPR3TefUXafvxSEdBo/h4HhMdhO/XPNDtESr0PAKShbh17l7fBbiQyWPvLKWZJcQmueojDtOmo3Bxc9FlynjTsvhFPNKR32M4B+wJB2eC4X72MmgLeFsbuJ+PAsYnhYkOaV7B9X7YRmCbKLg6LJESCdEv6fNmVvrGDi/yApihEVoHhBrRrp9EFQgdQhSj9BdSzcIV+FZiU3TFaVgtO5xGah5Zyx0gbXA0uAzSGUMuMrnnGF2MFvgo59e+S0Vf5PQ1KuO2rAKO8WRQMGpfF+ttkke7plWNwYcGQC1QBrJKUArb2Lxw4OIvaa+wS4uQmSB3DgETY IerhHGJI BgAnRLmiq9FESn4eZ0fCJXRv71vxfxfxJ1aWckDXCcbY6E2aViuOYFscBj3MsvM0YSIS8En6H0n9KLxD4ZRnY/e8olzYsHnQEsagdJ8mfoQqLM/kMAFbp0ERZ5kBTc6AYZNkm3LKQwzt/YEtok3EvP3Q5+Y/pJ909NsdRfrsNYHX00KtXTgOaycKJjAdSh/g/vM4z+vh3F7ndYdli70UpZBxmv0yKER/4gEQh8gpKvRuv/GPynMaaQ0Y39WmMY7EH0vSTp3rVGi1invn8HjWpZYViKVqi5Sh09e5LmwAuGAyzoMEmm/ZNI2Y5iwcd4Y1wk62/ 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 (23/06/19 17:35), Alexey Romanov wrote: > > We use a variable of type unsigned int to store the offset > of the first object at the subpage In turn, the offset cannot > exceed the size of PAGE_SIZE, which is usually 4096. Thus, > 12 bits are enough to store the offset. [..] > If the page size is 4Kb It's certainly not a given. PAGE_SIZE is architecture specific. PAGE_SIZE_16KB and PAGE_SIZE_64KB would be simple examples, but there are, apparently, architectures that even can have PAGE_SIZE_256KB.