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([2a01:4b00:bd21:4f00:7cc6:d3ca:494:116c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42cb7fb919bsm33941871f8f.34.2025.11.25.04.35.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 25 Nov 2025 04:35:08 -0800 (PST) Message-ID: <1f8b5e97-1f3c-46f8-8328-449c159b7d66@gmail.com> Date: Tue, 25 Nov 2025 12:35:06 +0000 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC v2 00/11] Add dmabuf read/write via io_uring To: Anuj gupta Cc: linux-block@vger.kernel.org, io-uring@vger.kernel.org, Vishal Verma , tushar.gohad@intel.com, Keith Busch , Jens Axboe , Christoph Hellwig , Sagi Grimberg , Alexander Viro , Christian Brauner , Andrew Morton , Sumit Semwal , =?UTF-8?Q?Christian_K=C3=B6nig?= , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org References: Content-Language: en-US From: Pavel Begunkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/24/25 13:35, Anuj gupta wrote: > This series significantly reduces the IOMMU/DMA overhead for I/O, > particularly when the IOMMU is configured in STRICT or LAZY mode. I > modified t/io_uring in fio to exercise this path and tested with an > Intel Optane device. On my setup, I see the following improvement: > > - STRICT: before = 570 KIOPS, after = 5.01 MIOPS > - LAZY: before = 1.93 MIOPS, after = 5.01 MIOPS > - PASSTHROUGH: before = 5.01 MIOPS, after = 5.01 MIOPS > > The STRICT/LAZY numbers clearly show the benefit of avoiding per-I/O > dma_map/dma_unmap and reusing the pre-mapped DMA addresses. Thanks for giving it a run. Looks indeed promising, and I believe that was the main use case Keith was pursuing. I'll fix up the build problems for v3 -- Pavel Begunkov