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 57F95C636D4 for ; Fri, 10 Feb 2023 19:49:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233428AbjBJTt0 (ORCPT ); Fri, 10 Feb 2023 14:49:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233537AbjBJTtZ (ORCPT ); Fri, 10 Feb 2023 14:49:25 -0500 Received: from mail-pf1-x42f.google.com (mail-pf1-x42f.google.com [IPv6:2607:f8b0:4864:20::42f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5AD677FEDC for ; Fri, 10 Feb 2023 11:48:45 -0800 (PST) Received: by mail-pf1-x42f.google.com with SMTP id d4so924994pfo.4 for ; Fri, 10 Feb 2023 11:48:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=fYTx4XvBOSsueNyLOIdpWr5U8lWZijTLj9xr3oRSm+E=; b=caDtprRmnqs7qjEJ6kuMrvA/jDCyeZfB15SohMIO11wYpHzx62as+u5JQYI2u8AyB5 Xy+Cbgas/SllQ49rHZGqZ952xfhRW8KVMEdF736i8OexY8hCfb4e1xdgsATLWS0RK4Kt eZT539S2+7Ctfd2bMX5zIoYvyC2VPadGHS4LvuEUrpPgAr0XkNEfzv4BZPg4cyxvJiPq u+dBlBtOF37BpWhhMeiqIs//A5phJdaENmeLY6IZaNxyQIbYbMujFXtSAoW3WHXjUkAm Aa6LgYyf2X1n6yPcFH46Q/xCsKI+wkJ/8N8J31Zl8NCUFcZ/Zsf1E1XN1JZqiw+LH00S YZ2A== 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:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=fYTx4XvBOSsueNyLOIdpWr5U8lWZijTLj9xr3oRSm+E=; b=268QxbDnxIcv0x65QPTEYEh9Hig4+DDov+2ufz64TfdqRXjT41/HHEPvSjKftpIMJc xRoDq2kj1FYPkNDIivm7LW8kr21AtINy4PMy9C3ZNGETqpoxvwPwDFZdxP0mK44MDigw epydw4u/74ywibtSmi1q2k1FhFMEDY59W5Qtvmj7dRXfLKyPb15e+9mP52YpfMnyeH+D uwfdOpqvouF5+MermYsqvpMca6n7W1+bwiFvKijYH1jLJJO0a5CKYtE2CBNNv0AsRqW2 3BnsVdai6O8MuPCKQqC8aseDQzOkFSfjl+XgoMz/S0bKP8l1yxDYMQFPknv9Q+1OFq1l jXSQ== X-Gm-Message-State: AO0yUKUsk+CW1dllO6I9zkEtI0M7kZT9SnNdRBnWS+UrQn0MDvRhuCoV ZQ+eVGEtqZpPKgPlA9zoQ7JSUw== X-Google-Smtp-Source: AK7set9l6RI7OIoQT77hlj4mEluI9EtAV/yEoHCems8NI36dW4yRIG5NRmi5GwoSrWnitnWNFBRhoA== X-Received: by 2002:a62:86c1:0:b0:5a8:5166:ca40 with SMTP id x184-20020a6286c1000000b005a85166ca40mr6298398pfd.3.1676058463120; Fri, 10 Feb 2023 11:47:43 -0800 (PST) Received: from [192.168.1.136] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id t18-20020a62ea12000000b005a851e6d2b5sm3584532pfh.161.2023.02.10.11.47.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Feb 2023 11:47:42 -0800 (PST) Message-ID: <8b1c3057-cc74-6169-c59a-283595eb46f0@kernel.dk> Date: Fri, 10 Feb 2023 12:47:40 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [LSF/MM/BPF ATTEND][LSF/MM/BPF Topic] Non-block IO To: Bart Van Assche , Kanchan Joshi , lsf-pc@lists.linux-foundation.org Cc: linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, io-uring@vger.kernel.org, hch@lst.de, kbusch@kernel.org, ming.lei@redhat.com References: <20230210180033.321377-1-joshi.k@samsung.com> <69443f85-5e16-e3db-23e9-caf915881c92@acm.org> Content-Language: en-US From: Jens Axboe In-Reply-To: <69443f85-5e16-e3db-23e9-caf915881c92@acm.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 2/10/23 11:18?AM, Bart Van Assche wrote: > 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". Sorry no, IOMMU cost is definitely not a solved problem, it adds considerable overhead. Caveat that I didn't read that paper, but speaking from practical experience. Let's not be naive here. -- Jens Axboe