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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 99FB4C4338F for ; Fri, 13 Aug 2021 16:29:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A06460EB2 for ; Fri, 13 Aug 2021 16:29:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234367AbhHMQ3v (ORCPT ); Fri, 13 Aug 2021 12:29:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36780 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235578AbhHMQ3v (ORCPT ); Fri, 13 Aug 2021 12:29:51 -0400 Received: from mail-pj1-x1032.google.com (mail-pj1-x1032.google.com [IPv6:2607:f8b0:4864:20::1032]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 19B2BC061756 for ; Fri, 13 Aug 2021 09:29:24 -0700 (PDT) Received: by mail-pj1-x1032.google.com with SMTP id w14so16025652pjh.5 for ; Fri, 13 Aug 2021 09:29:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=981c++31h9aesWwD/srk9/ifGKIkjjhoKMVzdVL8juA=; b=Vh2kT26FwlSB5AxFvO27FqqhSuXplfamhh+pHFmahiv5ilRi/NWOBHXFR65u2vECYj DCgEhseFX3QT+r212b5BFZWi/4yLDQVNS0zAmE5nPP/1GR1HI9w6DiRXtMh9U36E+3mz 3B473m5GvLd+WY6bPhQiDyhVawu73tG2UzWHNlzPOX71LFWqmmGGu+GMuk/89EO6jgpX lr1lEugnfE0NXa2YeuzTXKF4gELBmwQBBdzZ0g/Gud5f66YRbUDfxx/syhjoRS8r5XpC q9nxaOGcihVUTkYr7gzaPqrZI0DWLuh+cqOBDvYR2Rq1RlxLi3TnhqDzAaAaF0DhYypB 56tQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=981c++31h9aesWwD/srk9/ifGKIkjjhoKMVzdVL8juA=; b=A2KpVoxmckQ0dSLBATAxb16OLbW8Qyel14ekXs7aXp+9bppP5kijNkWNgU8iLOL6wj I4VMe2BYlKhf4RhYXkyHqJQk3qTbbBhdewFQBI+EdPpdqA3TOKtF4AZT6P7IZYCXXEvi 6DD0WwuucdxWHISBmQaDJVHK2A1/N5ripuml7YjJC1maiL9vaaarmNLDgaiJJTgPawg/ YcoHjd37sAmJoGwjNVGUbXW4gJ1yX24LaYuyi1UJAuwFt3i7YCfUT1V0mm9zyoqGKHzh g60AQ2vjMrzzWCTFI/McI/7yRgV+29Vrm5LdCCQhc9kK1EZfOTQkLZZT6tfb88jAaTX5 TnzA== X-Gm-Message-State: AOAM533UDO0TLye4id5UBysWEDUJ1dfXovUE/gMnQs7wxUhorvp7nJAK ujS4HCV29BwjXSoqMIFSszY= X-Google-Smtp-Source: ABdhPJzRCXEnPCUGG0FCtoIaT/0bAzGbPdNUyszNn7flDSG8PRHvr6S8+SljJ+0zLcWazAN4X2srfg== X-Received: by 2002:a17:902:e74c:b0:12d:93b2:25f2 with SMTP id p12-20020a170902e74c00b0012d93b225f2mr2761884plf.8.1628872163508; Fri, 13 Aug 2021 09:29:23 -0700 (PDT) Received: from localhost ([2620:10d:c090:400::5:e44d]) by smtp.gmail.com with ESMTPSA id c26sm3269732pgl.10.2021.08.13.09.29.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Aug 2021 09:29:22 -0700 (PDT) Sender: Tejun Heo Date: Fri, 13 Aug 2021 06:29:18 -1000 From: Tejun Heo To: Damien Le Moal Cc: Bart Van Assche , Jens Axboe , "linux-block@vger.kernel.org" Subject: Re: [PATCH block-5.14] Revert "block/mq-deadline: Add cgroup support" Message-ID: References: <035f8334-3b69-667d-be91-92dcab9dc887@acm.org> <00e13a7b-6009-a9d7-41ba-aae82f5813de@acm.org> <631e7e18-52ca-9bec-0150-bac755e0ff24@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hello, Damien. On Fri, Aug 13, 2021 at 02:18:04AM +0000, Damien Le Moal wrote: > Command duration limits (CDL) and Sequestered commands features are being > drafted in SPC/SBC and ACS to give the device better hints than just a on/off > high priority bit. I am currently prototyping these features and I am reusing > the ioprio interface for that. Here is how this works: And I think ioprio would be the right interface for it, combined with some mechanism which can limit which class can take up how many of the available command slots. Without that, it'd be really easy for anyone to saturate the command queues and expressing priorities inside the device won't do much. > CDL can completely replace the existing binary on/off NCQ priority in a more > flexible manner as the user can set different duration limits for high vs low > priority. E.g. high priority is equivalent to a very short limit while low > priority is equivalent to longer or no limits. The problem with complex optional hardware features is often the accompanying variability in terms of availability, reliability and behavior. The track record has been pretty sad. That isn't to say this won't be useful for anybody but it'd need careful coordination in terms of picking hardware vendor and model and ensuring vendor support, which kinda severely limits the usefulness. Thanks. -- tejun