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Mon, 24 Nov 2025 05:36:32 -0800 (PST) Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: In-Reply-To: From: Anuj gupta Date: Mon, 24 Nov 2025 19:05:54 +0530 X-Gm-Features: AWmQ_bkynwx2lMdwns4GsIfVtYmI6CqY40r8-Afst6-_o29b3r6t6sfqC-dnOGU Message-ID: Subject: Re: [RFC v2 00/11] Add dmabuf read/write via io_uring To: Pavel Begunkov 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 Content-Type: text/plain; charset="UTF-8" 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. -- Anuj Gupta