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Howlett" , Lorenzo Stoakes , David Hildenbrand , Mike Rapoport , Zi Yan , Minchan Kim Subject: Re: [PATCH] mm: Add ARCH_FORCE_PAGE_BLOCK_ORDER to select page block order Message-ID: <20250502113733.GA29622@willie-the-truck> References: <20250501052532.1903125-1-jyescas@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: CBC89C0005 X-Stat-Signature: mcwf3fp73co4ucormcccrm7m4567ue3c X-HE-Tag: 1746185861-192286 X-HE-Meta: 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 yITuH+jH hvtYooJj14h370gQr/O7IMDKJ68r2wc0QGT0vpxj2bd5ke1YYeMzOeLsuLn1U2BvucVbUPXdK8Flxh+7n9ecSzgx4zTn/z1NopI9IrBnsX282FafhNkrG4aBXeay3gzhoByUw/8E8Xj2mypREKN645y8Au+DtoqIuKyQxvLM48VscGjTeEKjQfRTHVWLePkCMSC7naNMhn3/9mIDma7U9lZ8WykD+T13gEF6XNef0/HExyW+/I/wUy1yw6ecVoaB7x2O40fEBrLAXURamBWBv99VvOaJd7yS9S+8jJf/3cUsCwMAiS8P8F+KkLg== 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 Thu, May 01, 2025 at 07:38:13PM +0100, Matthew Wilcox wrote: > On Wed, Apr 30, 2025 at 10:25:11PM -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. > > Sure, but why would any architecture *NOT* want to set this? > This seems like you're making each architecture bump into the problem > by itself, when the real problem is that the CMA people never thought > about this and should have come up with better defaults. Yes, I agree. It would be nice if arm64 wasn't the odd duck here. You'd think Power and Risc-V would benefit from similar treatement, if nothing else. Will