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=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 F10BBC73C66 for ; Sat, 13 Jul 2019 21:53:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C6BC420848 for ; Sat, 13 Jul 2019 21:53:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="GBKoJIbD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727978AbfGMVxd (ORCPT ); Sat, 13 Jul 2019 17:53:33 -0400 Received: from mail-pl1-f195.google.com ([209.85.214.195]:33308 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728117AbfGMVxd (ORCPT ); Sat, 13 Jul 2019 17:53:33 -0400 Received: by mail-pl1-f195.google.com with SMTP id c14so6426428plo.0 for ; Sat, 13 Jul 2019 14:53:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=b7knXnl2++CFgl1JI0y7AdoYd0cxeaaz3u9LcN6Nzc0=; b=GBKoJIbDYL40ytBfLjjdyrhV6Xa17aiOXF67nY5wZGnfJ36o0brcuBzdRHb48joauj hsoENFwjmNy9W5NUlp7Bzljv5zQ3xRVgF9erHRUUoVJvvPELOK3qW0Q2BYNVWFs7b43i nQz5V2q7t/+u4b15AqHufZ3QrZOfJwX3PY47fYbuq+bmJz2LJGIJW0cGX0lDX5f5WJ1f +TCsGPV/gnprSXVI/j2ybfZgZm5cEhBxITQUHigpN8bq29ww8d0yoCPXOfpANPUmHbFZ egb699NxOku++AH5+aKv66wZ2F1+reJwKuByTEsNWV1KrFNZKeRjEggiF6SuHRhYj+ne o3Gw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=b7knXnl2++CFgl1JI0y7AdoYd0cxeaaz3u9LcN6Nzc0=; b=AisDMb/MUXKxL/jdj9/Fvx5xR7rAGLa/IfKLLxIGgbNGfW/o/rVr60zWfKm5qO+3dD ll8m0Agh9ZlvMvK0AYKLfrPGvkC1t9RphvTFBi9n1W1jGnDRZFrEo64FAmhjLaRHl8px uDwey5GJ1YYxZRWj2XzteSRj9XaT2+BEmKVYvNMX4O7q9x5EhtVk+o02ZAI3Hs23Yevt HA2s2GIBTetgaLNhhKZAHSMfN0tD9QkfP6celI6Wrxub81Fiof0d6TeKxZaHLjz5frB3 K6Y+xslxZbrKSF5s3ogMMl2kG8IrWMjp2Dozoa5O4gLQhchEAKzgQF4I4JHxkNvM49pl 2dGg== X-Gm-Message-State: APjAAAVx4FWAK/bXDbdiIlMD+NzpQR6uJeo4WaOlTMNHap7jeLCi6r+q r56rBGpTZwbrSjqgidjYgC0pzwfOifE= X-Google-Smtp-Source: APXvYqx02JUB1gQ7VYbzSEBNpDUTlbVYzD3L8YrvaiHHDUeAEyQQnYdrydPsxOKGRUV4Lyy9Gx0vDA== X-Received: by 2002:a17:902:8547:: with SMTP id d7mr20064189plo.171.1563054811664; Sat, 13 Jul 2019 14:53:31 -0700 (PDT) Received: from [192.168.1.121] (66.29.164.166.static.utbb.net. [66.29.164.166]) by smtp.gmail.com with ESMTPSA id d14sm17326936pfo.154.2019.07.13.14.53.29 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 13 Jul 2019 14:53:30 -0700 (PDT) Subject: Re: [PATCH] block: elevator.c: Check elevator kernel argument again To: Marcos Paulo de Souza , linux-kernel@vger.kernel.org Cc: "open list:BLOCK LAYER" References: <20190713035221.31508-1-marcos.souza.org@gmail.com> From: Jens Axboe Message-ID: <75c5681a-389f-cfaf-7f3f-31a2daec9da4@kernel.dk> Date: Sat, 13 Jul 2019 15:53:28 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190713035221.31508-1-marcos.souza.org@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 7/12/19 9:52 PM, Marcos Paulo de Souza wrote: > Since the inclusion of blk-mq, elevator= kernel argument was not being > considered anymore, making it impossible to specify a specific elevator > at boot time as it was used before. > > This is done by checking chosen_elevator global variable, which is > populated once elevator= kernel argument is passed. Without this patch, > mq-deadline is the only elevator that is can be used at boot time. > > Signed-off-by: Marcos Paulo de Souza > --- > > I found this issue while inspecting why noop scheduler was gone, and > so I found that was now impossible to use a scheduler different from > mq-deadeline. > > Am I missing something? Is this a desirable behavior? Just google, I'm sure 2-3 discussions on this topic will come up. tldr is that the original parameter was a mistake and doesn't work at all for multiple devices. Today it's even worse, as we have device types that won't even work properly with any scheduler, liked the zoned devices. The parameter was never enabled for blk-mq because of that, and hence died when the legacy IO path was scrapped. It's not coming back. -- Jens Axboe