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=-2.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 836CDC43387 for ; Tue, 18 Dec 2018 16:41:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 53452218A2 for ; Tue, 18 Dec 2018 16:41:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545151295; bh=f7YDmal4zaS59t4FNh85WqctGyssNzqUDY+0AA/M6pA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=SZiDNgL1tB4tmWnhjeUM1Pm3tVsyWpVlEIeesddc9tIQOMznFRDMfX0N2TQl/VE9k U6KTg8e9TC6Qv8AB+bd8J1X5JE/jdNh/fq0aHk4Gzcfls8zg0N82ma+XgixAy/L9yn kOaox8RjO3hyIdjsbrfGTaOml6ob+cDba1IhS6NQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727551AbeLRQld (ORCPT ); Tue, 18 Dec 2018 11:41:33 -0500 Received: from mail-yb1-f196.google.com ([209.85.219.196]:41097 "EHLO mail-yb1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727529AbeLRQla (ORCPT ); Tue, 18 Dec 2018 11:41:30 -0500 Received: by mail-yb1-f196.google.com with SMTP id e124so6701759ybb.8; Tue, 18 Dec 2018 08:41:29 -0800 (PST) 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:user-agent; bh=Qxr/PEmJFsRrEklCc2G+CWcsbCOLd3hDZQ0GvBRgCew=; b=pvDaeC2cbDIqoVcA3a91jug0vWkjNpchLP/2I2Se4eWplDu/fuTKeXSS/VJV8ywV1q i9aIGZnHhCRXA6OCtBTff+pbjuA3yI/AmyteGwyk/ELfIMyGyjOd0u5u8a5SOEmS9IyO loJmL9R+FyAQmPEtz4V0PzR8dCuRwlkIpRyVKvJREujIeYdchZnzile8RH0l1A6BZpRI j68L6pqFN65vlqESWiDbK4M/bnJifR3Gc5TIrP1uASGG+6OO85l6m1TH3ogYBiDfjiyS V34/ZTwVwcy9A7pkAhG8JbqhOMNOXb7TEejxdnWjRpFX3IqFfOhMCPYq56irF+sNyjFe wQow== 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:user-agent; bh=Qxr/PEmJFsRrEklCc2G+CWcsbCOLd3hDZQ0GvBRgCew=; b=U6rzVB3Ub3haAzvsHdsrHVSv+vcUqGYBoTD5Qnr+eRphwWtY1pnlzSEnGUyR1FNNme kPKcXrO54YkxnzsGrywufaLgDkVxMIKLeBBGUWNmHRjme0Jz6KFaPTt85uOEB8efp2CW ed5ugY8A0kADJVUYKrkkBaQR9/D4uQV9o6nXlotS2JQSmRrgQUDS3BSUR90nEqsdR67x U3MOkxlJiogJ/l2Vp46ENJ1vQ1nxNDEpmGvPe+Gyjr//jmjG+76KHc8QgYmD3MT+lsj+ 9lKHju18oyzxE1hQehDN38kEoLBUMusBl+6al2GrI6BWNsSwjL2doyfJqSJXXBJvSgwl IacQ== X-Gm-Message-State: AA+aEWaNsV8pCJgDNlZPdbaChex4lBESPoCfndXYqEXOZIrjSzdtf1w1 xe7VdKEYK2ERfWZGnymlPqU= X-Google-Smtp-Source: AFSGD/XPNSc5mjbbY9XH59BLB/2z2usE7bQPynMjKTCa4gkvUWRUEqp3Xn2to4n3OUWAerQYf9dMCA== X-Received: by 2002:a5b:3d1:: with SMTP id t17mr17820633ybp.435.1545151288729; Tue, 18 Dec 2018 08:41:28 -0800 (PST) Received: from localhost ([2620:10d:c091:200::6:e01b]) by smtp.gmail.com with ESMTPSA id y83sm5015892ywd.65.2018.12.18.08.41.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Dec 2018 08:41:27 -0800 (PST) Date: Tue, 18 Dec 2018 08:41:26 -0800 From: Tejun Heo To: Paolo Valente Cc: Angelo Ruocco , 'Paolo Valente' via bfq-iosched , Jens Axboe , Greg Kroah-Hartman , Li Zefan , Angelo Ruocco , Dennis Zhou , Josef Bacik , Liu Bo , Bart Van Assche , Johannes Weiner , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ulf.hansson@linaro.org, linus.walleij@linaro.org, broonie@kernel.org, oleksandr@natalenko.name, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, Jonathan Corbet Subject: Re: [PATCH V2 00/10] unify the interface of the proportional-share policy in blkio/io Message-ID: <20181218164126.GX2509588@devbig004.ftw2.facebook.com> References: <20181119103424.3853-1-paolo.valente@linaro.org> <20181120162816.GV2509588@devbig004.ftw2.facebook.com> <25296DAE-73EC-46CC-9A98-A8B7E9017BB7@linaro.org> <7D7FAB43-5F62-4402-A9B3-E7C2E30AE680@linaro.org> <20181130184256.GI2509588@devbig004.ftw2.facebook.com> <5534B7D4-A5D9-4F44-9620-970A7F9EC140@linaro.org> <874A0232-2103-4364-BD88-F33B85D6A764@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <874A0232-2103-4364-BD88-F33B85D6A764@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Paolo. On Tue, Dec 18, 2018 at 08:48:10AM +0100, Paolo Valente wrote: > If Tejun cannot see any solution to his concern, then can we just > switch to this extension, considering that > - for non-shared names the interface is *identical* to the current > one; > - by using this new interface, and getting feedback we could > understand how to better handle Tejun's concern? > A lot of systems do use weights, and people don't even know that these > systems don't work correctly in blk-mq. And they won't work correctly > in any available configuration from 4.21, if we don't fix this problem. So, when seen from userland, how it should behave isn't vague or complicated. For a given device and policy type, there can be only one implementation active. It doesn't make sense to have two weight mechanisms active on one device, right? So, the interface should only present what makes sense to the user for both configuration knobs and statistics, and that'd be a hard requirement because we don't want to present confusing spurious information to userspace. There seemd to have been significant misunderstandings as to what the requirements are when this was discussed way back, so idk what the good path forward is at this point. Just keep the current names? Thanks. -- tejun