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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 110BAC4167B for ; Thu, 10 Dec 2020 20:19:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C392823D6B for ; Thu, 10 Dec 2020 20:19:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393768AbgLJUTX (ORCPT ); Thu, 10 Dec 2020 15:19:23 -0500 Received: from mx2.suse.de ([195.135.220.15]:36558 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390014AbgLJUTR (ORCPT ); Thu, 10 Dec 2020 15:19:17 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 03C95AC6A; Thu, 10 Dec 2020 20:18:32 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 4336CDA842; Thu, 10 Dec 2020 21:16:55 +0100 (CET) Date: Thu, 10 Dec 2020 21:16:55 +0100 From: David Sterba To: Nikolay Borisov Cc: Sidong Yang , linux-btrfs@vger.kernel.org Subject: Re: [PATCH] btrfs-progs: scrub: warn if scrub started on a device has mq-deadline Message-ID: <20201210201655.GG6430@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Nikolay Borisov , Sidong Yang , linux-btrfs@vger.kernel.org References: <20201205184929.22412-1-realwakka@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Dec 07, 2020 at 10:00:50AM +0200, Nikolay Borisov wrote: > On 5.12.20 г. 20:49 ч., Sidong Yang wrote: > > Warn if scurb stared on a device that has mq-deadline as io-scheduler > > and point documentation. mq-deadline doesn't work with ionice value and > > it results performance loss. This warning helps users figure out the > > situation. This patch implements the function that gets io-scheduler > > from sysfs and check when scrub stars with the function. > > NAK, use applications should be oblivious to what scheduler the admin > has set up. It's the responsibility of the admin to configure their > system properly, at most there could be a note that scrub is an > io-intensive process and leave the rest to the admin. If the admin is user of the machine, eg. on a desktop and starts a weekly scrub job that renders the machine unusable, then the warning makes sense. And actually this is the situation that happened and prompted updates to documentation and also the warning to make it more visible. That mq-deadline scheduler lacks ionice support is not nice, we're trying to minimize the impact at least.