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, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 24F0EC742A2 for ; Sun, 14 Jul 2019 04:00:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F178020644 for ; Sun, 14 Jul 2019 04:00:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bncUZlj2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726399AbfGNEAs (ORCPT ); Sun, 14 Jul 2019 00:00:48 -0400 Received: from mail-qk1-f195.google.com ([209.85.222.195]:42171 "EHLO mail-qk1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725283AbfGNEAs (ORCPT ); Sun, 14 Jul 2019 00:00:48 -0400 Received: by mail-qk1-f195.google.com with SMTP id 201so9301923qkm.9; Sat, 13 Jul 2019 21:00:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=C+RV+0t2aWNWIaDr884rCShvl4d1XlrRv+L4Pe0LIdg=; b=bncUZlj2UwsnM4lg7q3q6DAcLq3rf5IA9Zt0r1AOGUzbgCRxhk/X5M/GraYxyZ3vY3 el+uVYCr42dlw2/qERTjY/gMAzybe3fRYSjvGLRh2EEPX65QiuNebhnyUlfJ0KZGeRYf AkNrFquwBx2vyB6SGNxS5/eXGxLKh0wRHSNCHWF3JdKCTR7TegsDhCVt9Abq9AOpVUVa hgkU6TJRgguqEm1hV1DYe051PZBZ3zyizFHPkHXdJqElTYFoz6koPOal65IuZj6vuwx1 uTO2AI9pIhTpuSNpwFrKwO0/Txb/GXXhEdk1aq9dklR+Rh8M5zAC2P4LII464cNMSi6v 0bbg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=C+RV+0t2aWNWIaDr884rCShvl4d1XlrRv+L4Pe0LIdg=; b=NvWxGPHMe0XmaSQlXK3AtbFgkmUPlwR8IBwTFtgf018qJQxHcJQlXCxIWJDOXP2tU8 7aSWhkGd8a4WO18rbyMLnk3j64vMzOYsbebKPm9yv9iUJjY71Ek9ZSUqOhMGayiSGjn0 SKevMm5iNZN5wuoK9/n85is68PFsp/QFBPoLFJtqaiMuzhEjGR2GhCz6YeNaViQgOFx+ OrITBqiqeOeJ4A/BKXmDwnh3T3e1gyrFJI2VH2vod19MYe9hDp4duU0SFhuPEhaJ+Uhg iWzmWKer6caDJEouH4KPyuJvbSK0jc2nWKM5S3ub5iqsnTgvoNXFrGbIrJ4W3oY8uvxr bgUw== X-Gm-Message-State: APjAAAV4V8+/WQJNJxUk0f8K/7aW8IJ1JCCWM5gPvfsnXSYt2nJY5FDI Fr5GTp8i5Et1BHqS/3NthyEhkMCnnkY= X-Google-Smtp-Source: APXvYqwR3zBitPfMP6j5VloXIL1iUifK5UJMmS24W2MbNT+arbkJg1XSP7j7UhqSmrUhabuH5MMFPw== X-Received: by 2002:a05:620a:1097:: with SMTP id g23mr11879799qkk.185.1563076847251; Sat, 13 Jul 2019 21:00:47 -0700 (PDT) Received: from continental ([191.35.237.35]) by smtp.gmail.com with ESMTPSA id e8sm5792816qkn.95.2019.07.13.21.00.44 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Sat, 13 Jul 2019 21:00:46 -0700 (PDT) Date: Sun, 14 Jul 2019 01:01:18 -0300 From: Marcos Paulo de Souza To: Jens Axboe Cc: linux-kernel@vger.kernel.org, "open list:BLOCK LAYER" Subject: Re: [PATCH] block: elevator.c: Check elevator kernel argument again Message-ID: <20190714040118.GA19237@continental> References: <20190713035221.31508-1-marcos.souza.org@gmail.com> <75c5681a-389f-cfaf-7f3f-31a2daec9da4@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <75c5681a-389f-cfaf-7f3f-31a2daec9da4@kernel.dk> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 13, 2019 at 03:53:28PM -0600, Jens Axboe wrote: > 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. Thanks Jens. So it makes sense to remove all leftover code of elevator argument with some dead documentation about it, avoiding confusion about it in the future again. I will send some patches tomorrow. > > -- > Jens Axboe >