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[142.167.219.86]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6f4c74d3dcbsm53164536d6.50.2025.04.28.06.16.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Apr 2025 06:16:32 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1u9OLX-00000009TaN-1zxp; Mon, 28 Apr 2025 10:16:31 -0300 Date: Mon, 28 Apr 2025 10:16:31 -0300 From: Jason Gunthorpe To: Leon Romanovsky Cc: Luis Chamberlain , Marek Szyprowski , Jens Axboe , Christoph Hellwig , Keith Busch , Jake Edge , Jonathan Corbet , Zhu Yanjun , Robin Murphy , Joerg Roedel , Will Deacon , Sagi Grimberg , Bjorn Helgaas , Logan Gunthorpe , Yishai Hadas , Shameer Kolothum , Kevin Tian , Alex Williamson , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Andrew Morton , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-rdma@vger.kernel.org, iommu@lists.linux.dev, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, Niklas Schnelle , Chuck Lever , Matthew Wilcox , Dan Williams , Kanchan Joshi , Chaitanya Kulkarni Subject: Re: [PATCH v9 07/24] dma-mapping: Implement link/unlink ranges API Message-ID: <20250428131631.GB1213339@ziepe.ca> References: <2d6ca43ef8d26177d7674b9e3bdf0fe62b55a7ed.1745394536.git.leon@kernel.org> <20250427081312.GE5848@unreal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250427081312.GE5848@unreal> X-Rspamd-Queue-Id: D90CE160012 X-Stat-Signature: p131c5etdjomiu4spghokiwddqwzi1pi X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1745846193-806143 X-HE-Meta: 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 SSA== 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 Sun, Apr 27, 2025 at 11:13:12AM +0300, Leon Romanovsky wrote: > > So arch_sync_dma_for_device() is a no-op on some architectures, notably x86. > > So since you're doing this work and given the above pattern is common on > > the non iova case, we could save ourselves 2 branches checks on x86 on > > __dma_iova_link() and also generalize savings for the non-iova case as > > well. For the non-iova case we have two use cases, one with the attrs on > > initial mapping, and one without on subsequent sync ops. For the iova > > case the attr is always consistently used. > > I want to believe that compiler will discards these "if (!coherent && > !(attrs & DMA_ATTR_SKIP_CPU_SYNC)))" branch if case is empty. Yeah, I'm pretty sure it will Jason