From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DAABFC05027 for ; Fri, 10 Feb 2023 18:18:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232696AbjBJSSW (ORCPT ); Fri, 10 Feb 2023 13:18:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232822AbjBJSSU (ORCPT ); Fri, 10 Feb 2023 13:18:20 -0500 Received: from mail-pg1-f178.google.com (mail-pg1-f178.google.com [209.85.215.178]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3FD15A9C6; Fri, 10 Feb 2023 10:18:11 -0800 (PST) Received: by mail-pg1-f178.google.com with SMTP id x10so4278158pgx.3; Fri, 10 Feb 2023 10:18:11 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=CuIV2ZniuR6JiN7/4weCn+3flzvSdKoSszT4evfBW74=; b=0vM0dRsot13GlgKxdEPxm6rjvV2GAb8eN7CSctXm2vBi/Rn8lIJ1Si9O/zxeh7VMe4 kBW/6atqTzLpMCje+HOWfWEtNZ3wSfRrID2ugjqsWK0cOgY8GRsacs/5Bjn3LT2D7iQM tTU3LGKuaZphweIzbyztGJ9oJ9akdTnOMsom45BHOOqiIzvH9QagUzKAQ9La9C8PBfR/ vgvbHzIBOhCPVHjwEosioet79Wvtz0brAmZiDFrekvItPtrfeIlD4JqYZEa/jNZf9iLZ kvnJM1flst4XeM5LKST3dnuLUgokbXF2I+Mp3D7gC7iE7MO5jkb8/vZM45pBPXrdWtXq zIFA== X-Gm-Message-State: AO0yUKVyvxXJXZN0Worerzh+FXJNHovnqnmajX5D3Wk9yd61hejy+0MS kotu/QsNXT1hbIsJpewp8pagOBjIDBc= X-Google-Smtp-Source: AK7set9N6MjmZsXjybdAr+hJoPFSqTEoYhUaKedYxqLCBx2V8yPx0GxWd7g+wUZ3hObnC7poWBjmIw== X-Received: by 2002:a62:14d0:0:b0:5a8:5dcb:b775 with SMTP id 199-20020a6214d0000000b005a85dcbb775mr5120458pfu.14.1676053090955; Fri, 10 Feb 2023 10:18:10 -0800 (PST) Received: from [192.168.51.14] ([98.51.102.78]) by smtp.gmail.com with ESMTPSA id v9-20020a62a509000000b005941ff79428sm3645099pfm.90.2023.02.10.10.18.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Feb 2023 10:18:10 -0800 (PST) Message-ID: <69443f85-5e16-e3db-23e9-caf915881c92@acm.org> Date: Fri, 10 Feb 2023 10:18:08 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [LSF/MM/BPF ATTEND][LSF/MM/BPF Topic] Non-block IO Content-Language: en-US To: Kanchan Joshi , lsf-pc@lists.linux-foundation.org Cc: linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, io-uring@vger.kernel.org, axboe@kernel.dk, hch@lst.de, kbusch@kernel.org, ming.lei@redhat.com References: <20230210180033.321377-1-joshi.k@samsung.com> From: Bart Van Assche In-Reply-To: <20230210180033.321377-1-joshi.k@samsung.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 2/10/23 10:00, Kanchan Joshi wrote: > 3. DMA cost: is high in presence of IOMMU. Keith posted the work[1], > with block IO path, last year. I imagine plumbing to get a bit simpler > with passthrough-only support. But what are the other things that must > be sorted out to have progress on moving DMA cost out of the fast path? Are performance numbers available? Isn't IOMMU cost something that has already been solved? From https://www.usenix.org/system/files/conference/atc15/atc15-paper-peleg.pdf: "Evaluation of our designs under Linux shows that (1) they achieve 88.5%–100% of the performance obtained without an IOMMU". Thanks, Bart.