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Howlett" , Lorenzo Stoakes , David Hildenbrand , Mike Rapoport , Minchan Kim Subject: Re: [PATCH v3] mm: Add CONFIG_PAGE_BLOCK_ORDER to select page block order Message-Id: <20250506000133.ba44539dd517e4f54515751b@linux-foundation.org> In-Reply-To: <20250506002319.513795-1-jyescas@google.com> References: <20250506002319.513795-1-jyescas@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 49A03180012 X-Rspam-User: X-Stat-Signature: rfta8dbt5bdddmo6wqonpuyi1j8roub5 X-HE-Tag: 1746514895-92153 X-HE-Meta: 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 Btk0eaM5 RxrhMO6PdpLjauvR8xr5xLtr8EL2nEN6pa9SHngqwKqSL+Z8WPliqsSg3l/jFvu5rLv/+IwfvzdKFk/tAz8OOJHLflo/hxMAaZ+QKwdnFaK5Vg6MqhMZ4/aaLaUAR1H0bpCH6Muyn1Y9STVzeVQNXP9ghtpS1Xjc9g7+MENQOs+ZUpUuxHj9AuuVxbasJUECbsKTTavE2lG6svfcp0FNoEcQ1Th9TENXaU41mw3VhY9vgNQgFT6D667EMSNVknIyRBEHoDXJ3I/K6ppNM7OkidPRBtwajMou0ePOJXi9p4Fb+hti3iInnVWEfd7MgHE45IfBT 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 Mon, 5 May 2025 17:22:58 -0700 Juan Yescas wrote: > Problem: On large page size configurations (16KiB, 64KiB), the CMA > alignment requirement (CMA_MIN_ALIGNMENT_BYTES) increases considerably, > and this causes the CMA reservations to be larger than necessary. > This means that system will have less available MIGRATE_UNMOVABLE and > MIGRATE_RECLAIMABLE page blocks since MIGRATE_CMA can't fallback to them. > > The CMA_MIN_ALIGNMENT_BYTES increases because it depends on > MAX_PAGE_ORDER which depends on ARCH_FORCE_MAX_ORDER. The value of > ARCH_FORCE_MAX_ORDER increases on 16k and 64k kernels. > > ... > > +config PAGE_BLOCK_ORDER > + int "Page Block Order" > + range 1 10 if !ARCH_FORCE_MAX_ORDER > + default 10 if !ARCH_FORCE_MAX_ORDER > + range 1 ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER > + default ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER Do we really need to do this arithmetic within Kconfig? Would it be cleaner to do this at runtime, presumably when calculating pageblock_order?