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Mon, 15 May 2023 12:09:17 -0700 (PDT) Date: Mon, 15 May 2023 12:09:12 -0700 From: Isaac Manjarres To: Catalin Marinas Cc: Linus Torvalds , Arnd Bergmann , Christoph Hellwig , Greg Kroah-Hartman , Will Deacon , Marc Zyngier , Andrew Morton , Herbert Xu , Ard Biesheuvel , Saravana Kannan , Alasdair Kergon , Daniel Vetter , Joerg Roedel , Mark Brown , Mike Snitzer , "Rafael J. Wysocki" , Robin Murphy , linux-mm@kvack.org, iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, Petr Tesarik Subject: Re: [PATCH v3 00/13] mm, dma, arm64: Reduce ARCH_KMALLOC_MINALIGN to 8 Message-ID: References: <20221106220143.2129263-1-catalin.marinas@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 79ACA8000D X-Stat-Signature: gopws3tmi9qfp66uxxafohf7z8qfrjco X-HE-Tag: 1684177759-284615 X-HE-Meta: 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 Hrn6aaTn c2AG0+8dQ61rXbFFFku3PFyUnEPZnKDWyv6LggeQKe8wjxLh6p4mRD+Lf8eo8XeNZU7r6t2DHQUc2ImjMRAxu3rI+UaZf+BOY5XGg8ZyvlmgMIn4RUNYhWbCD0r4ugTCv9Mr20RDWXAaOkfQGdsfh9l9BegbCpiUMmB6HCLlSLT2A7QQgAbqy6Z9xk+ynxKc0N2CoalIYyX4HGe+kDhIooNGYwwMaRFLK8ipZ5bwW5Ut7aAYy23QmLDPop9tKrukEBlQ6G0BIpFnXNltZ456gbmzJvfkIqrS39rlsypVFLM+hrc5PbTxgxC3G/wiQexPC/D7lLsDE4HA4VXECdyk/noo+Z1UH5FAxs0NEzmKCOJvserM30Dzz/ZFWZ2NHly2syY1wt3pVJaTwTCsKN/M0S+KPdS4c5oOWbG8y 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 Wed, Apr 19, 2023 at 05:06:04PM +0100, Catalin Marinas wrote: > I rebased it locally but the last stumbling block is sorting out the > iommu bouncing. I was hoping Robin Murphy can lend a hand but he's been > busy with other bits. I'll repost the series at 6.4-rc1. Hey Catalin, just following up on this. I think it might be worthwhile to split this series into two series: Series 1: Decouple ARCH_KMALLOC_MINALIGN from ARCH_DMA_MINALIGN, and use the cacheline size to determine the minimum kmalloc alignment. Series 2: Lower the minimum kmalloc alignment to 8 bytes by adding support for using SWIOTLB to bounce unaligned kmalloc buffers for DMA transactions. Dividing the patches as such has the advantage of lowering the minimum kmalloc alignment to 64 bytes on many ARM64 systems while the work for lowering the minimum alignment to 8 bytes proceeds. This provides a noticeable decrease in the slab memory footprint (e.g. I observed a 15 MB decrease in slab usage on a device I was using). What are your thoughts on this? --Isaac