linux-kernel - Re: [RFC v2 00/11] Add dmabuf read/write via io

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1f8b5e97-1f3c-46f8-8328-449c159b7d66@gmail.com>
Date: Tue, 25 Nov 2025 12:35:06 +0000
From: Pavel Begunkov <asml.silence@...il.com>
To: Anuj gupta <anuj1072538@...il.com>
Cc: linux-block@...r.kernel.org, io-uring@...r.kernel.org,
 Vishal Verma <vishal1.verma@...el.com>, tushar.gohad@...el.com,
 Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...nel.dk>,
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
 Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Sumit Semwal <sumit.semwal@...aro.org>,
 Christian König <christian.koenig@....com>,
 linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
 linux-fsdevel@...r.kernel.org, linux-media@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [RFC v2 00/11] Add dmabuf read/write via io_uring

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