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Tue, 16 May 2023 11:19:27 -0700 (PDT) Received: from google.com ([2620:15c:2d:3:fd80:d223:d66f:530f]) by smtp.gmail.com with ESMTPSA id x5-20020a170902b40500b0019a6cce2060sm15837904plr.57.2023.05.16.11.19.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 May 2023 11:19:26 -0700 (PDT) Date: Tue, 16 May 2023 11:19:22 -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: rspam02 X-Rspamd-Queue-Id: 3EDDD40016 X-Stat-Signature: d76793iom9wu19c555g5j5gaeofe8imo X-HE-Tag: 1684261168-557854 X-HE-Meta: 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 Z9EbUZqZ QKzamAsbmBPh2qTZa9HzZ2OqV3KcKbu33Jeouzhe9NkQJitV6jmcWqrVGy+QLJ+pVP8oDPbXlnFNiOYNf24plSdhmiGhlh74ulWi8Br3zDMNyS96tKsH/LEHH2DM3SViGbSUp/1fLR5U+PUfSfbRyYInfuFcK2WD6vzwCCehrFEBkkLmXzhFWgS9TKCO4CIHTt4dTR+8PPEkeJTVGRTEEB6twnBUzCYB3BArSL//YVyNWP721Qv5xw/LQDsAZj093YFxV/OwhMtda3FmsTEHNd3UrX1FIMW1vG3EYbWBiNrJ7cdUBt5QPU6W70FXRcRG19ujNuo36J/UKYoj790z8o/8Uno1rQXw4oWDAIlDYl7gaQnefqsCmEZBkk15a8vVYRjSt1rBlouONf2dRM0YqTQmMZp00mp3egDlf 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 Tue, May 16, 2023 at 06:19:43PM +0100, Catalin Marinas wrote: > On Mon, May 15, 2023 at 12:09:12PM -0700, Isaac Manjarres wrote: > > 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. > > I attempted "series 1" some time ago and the discussion led to the > combined approach (i.e. don't bother with limiting kmalloc minimum > alignment to cache_line_size() but instead bounce those small buffers). > In my series, I still have this fallback in case there's no swiotlb > buffer. > I'll post a new series this week (including DMA bouncing) but I'll try > to move the bouncing towards the end of the series in case there are > more discussions around this, at least the first part could be picked > up. Thanks Catalin! I think restructuring the series as you're suggesting makes sense. At least being able to pick up the first part of the series would be great, since it will have a positive impact on the memory footprint for a lot of devices. This also helps alleviate some of the memory overhead for devices that move from a 32-bit ARM kernel to a 64-bit ARM kernel. The second part can continue to be refined until the SWIOTLB and IOMMU bounce buffering refactor is complete. -Isaac