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 0E4C9C433F5 for ; Wed, 16 Mar 2022 14:50:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233040AbiCPOwL (ORCPT ); Wed, 16 Mar 2022 10:52:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236677AbiCPOwK (ORCPT ); Wed, 16 Mar 2022 10:52:10 -0400 Received: from mail-wr1-f45.google.com (mail-wr1-f45.google.com [209.85.221.45]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A45A35F4C6; Wed, 16 Mar 2022 07:50:56 -0700 (PDT) Received: by mail-wr1-f45.google.com with SMTP id x15so3286264wru.13; Wed, 16 Mar 2022 07:50:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=bI4ZhjQL8dIuJvz21TfUD5JbGeAx7Qdq2Uugzf6XgB0=; b=T8eaUq22SmrqQEkehJYK1KwHHKCraiQH+4hHcqgNBQs+Scx79ozCBs1JN48AnC9eP1 5EUEn4qjPWOW2TbrGeYkC2iLd0GC6DDMqbvmjsWZnf3XbKjH4Luhifn4MOmifOlTfCWR nu7xZ4PzuwCbBITZUatpCMQA/OdZMGPyTZSbip6YaX7d9Q6Dr8fG433rs7yAS1B31FF7 mflix6gZ/mx7PVKzRv76SOvWLGJBCT09PPCaLwIqvxFjQYSzlPS2I0dGL6u6jCHLj20b 36K3MSO1TOnq5ci4kDV8DMTPYs3I/5QsdLcVr+dKc9DA3jWLIKuOi4zYvGxlGLWPjAyM I80g== X-Gm-Message-State: AOAM533EY5CgNqtUTieYVFhwclZbpMGUF4U7O54hDoSm6lirKT40g63Y i84O2P/Wwrm6e8rb6mlRS38= X-Google-Smtp-Source: ABdhPJzrRH5zBsn9fYkNcZjd08EnDBOCdVlS4Q3hFeb7W2Pq1bG2CpbUzWEW5D36WNgcL+UcKvbCng== X-Received: by 2002:a5d:6c6b:0:b0:1ea:77ea:dde8 with SMTP id r11-20020a5d6c6b000000b001ea77eadde8mr271610wrz.690.1647442255234; Wed, 16 Mar 2022 07:50:55 -0700 (PDT) Received: from [192.168.64.180] (bzq-219-42-90.isdn.bezeqint.net. [62.219.42.90]) by smtp.gmail.com with ESMTPSA id r4-20020a05600c35c400b00389f368cf1esm513959wmq.40.2022.03.16.07.50.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Mar 2022 07:50:54 -0700 (PDT) Message-ID: <28b53100-9930-92d4-ba3b-f9c5e8773808@grimberg.me> Date: Wed, 16 Mar 2022 16:50:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH 05/17] nvme: wire-up support for async-passthru on char-device. Content-Language: en-US To: Jens Axboe , Kanchan Joshi Cc: Kanchan Joshi , Christoph Hellwig , Keith Busch , Pavel Begunkov , io-uring@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, sbates@raithlin.com, logang@deltatee.com, Pankaj Raghav , =?UTF-8?Q?Javier_Gonz=c3=a1lez?= , Luis Chamberlain , Adam Manzanares , Anuj Gupta References: <20220308152105.309618-1-joshi.k@samsung.com> <20220308152105.309618-6-joshi.k@samsung.com> <7a123895-1102-4b36-2d6e-1e00e978d03d@grimberg.me> <8f45a761-5ecb-5911-1064-9625a285c93d@grimberg.me> <20220316092153.GA4885@test-zns> <11f9e933-cfc8-2e3b-c815-c49a4b7db4ec@grimberg.me> <3ed01280-5487-7206-a326-0cd110118b65@grimberg.me> <666deb0e-fa10-8a39-c1aa-cf3908b3795c@kernel.dk> From: Sagi Grimberg In-Reply-To: <666deb0e-fa10-8a39-c1aa-cf3908b3795c@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org >> [...] >> >>> Got it, thanks. Passthrough (sync or async) just returns the failure >>> to user-space if that fails. >>> No attempt to retry/requeue as the block path does. >> >> I know, and that was my original question, no one cares that this >> interface completely lacks this capability? Maybe it is fine, but >> it is not a trivial assumption given that this is designed to be more >> than an interface to send admin/vs commands to the controller... > > Most people don't really care about or use multipath, so it's not a > primary goal. This statement is generally correct. However what application would be interested in speaking raw nvme to a device and gaining performance that is even higher than the block layer (which is great to begin with)? First thing that comes to mind is a high-end storage array, where dual-ported drives are considered to be the standard. I could argue the same for a high-end oracle appliance or something like that... Although in a lot of cases, each nvme port will connect to a different host... What are the use-cases that need this interface that are the target here? Don't remember seeing this come up in the cover-letter or previous iterations... > For passthrough, most of request types should hit the > exact target, I would suggest that if someone cares about multipath for > specific commands, that they be flagged as such. What do you mean by "they be flagged as such"?