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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B0DCEC77B7C for ; Thu, 11 May 2023 15:38:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238765AbjEKPiI (ORCPT ); Thu, 11 May 2023 11:38:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237708AbjEKPiH (ORCPT ); Thu, 11 May 2023 11:38:07 -0400 Received: from mail-pf1-f175.google.com (mail-pf1-f175.google.com [209.85.210.175]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 643674C38; Thu, 11 May 2023 08:38:06 -0700 (PDT) Received: by mail-pf1-f175.google.com with SMTP id d2e1a72fcca58-6439f186366so5435871b3a.2; Thu, 11 May 2023 08:38:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1683819486; x=1686411486; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=EZSuUDNZroiyxm8tSJ9/WgOQoub/MYxlf8xCitRpuzE=; b=E3cXAISAw9Bot++cvZ0EXW1inQ7B/pPWva41TqvasvmiaRY3nQTg70JGfGFkhbTCJU N9VFXdvDw3+M0nHQv8Ct+Vi8Yo20EcsEAnquARCSWAeTR10GPS1X6OjMpd+AtsdJ53N6 VS/Wn/R2Q11gRh2ao5alul6MU1NDIw3LpQiqumjzZML55D/zKtQyIKZelktSOBndPYx8 5ayZbzKtCWRMpgRlXUFbd6F1qaMimR6gRZdBEd4Ul4U1OBXljZeVLZjrvHJLgBcc/YaY Us36MTQ93BhG1zPDyD14okjZ0Z/zr68z07t+gw5Sp5HEQBEa/3VWShS+Pe+CkleUYTQx 8n1A== X-Gm-Message-State: AC+VfDw3x2sH7JXnskBzStiKoEDJv+H47UuflvFcnWd7VjM078zPTgsG k8ZOckdLtGGZcX1jIWpV8BWS66AvQJk= X-Google-Smtp-Source: ACHHUZ4yVECYtD+qVm4EPWXQ7n+M0L0oJ8Y1QiJhaT60VoEzwjnc6YrVie/FMwn3rdeYFmeiM417FQ== X-Received: by 2002:a05:6a00:14d0:b0:63d:2f13:1f3 with SMTP id w16-20020a056a0014d000b0063d2f1301f3mr29540905pfu.33.1683819485772; Thu, 11 May 2023 08:38:05 -0700 (PDT) Received: from [172.20.11.151] ([173.214.130.133]) by smtp.gmail.com with ESMTPSA id n1-20020aa78a41000000b0064550f76efesm5499494pfa.29.2023.05.11.08.38.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 May 2023 08:38:05 -0700 (PDT) Message-ID: Date: Thu, 11 May 2023 08:38:04 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH 2/2] ufs: don't use the fair tag sharings Content-Language: en-US To: Christoph Hellwig , Ed Tsai Cc: axboe@kernel.dk, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, martin.petersen@oracle.com, stanley.chu@mediatek.com, peter.wang@mediatek.com, chun-hung.wu@mediatek.com, alice.chao@mediatek.com, powen.kao@mediatek.com, naomi.chu@mediatek.com, wsd_upstream@mediatek.com References: <20230509065230.32552-1-ed.tsai@mediatek.com> <20230509065230.32552-3-ed.tsai@mediatek.com> From: Bart Van Assche In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 5/11/23 08:34, Christoph Hellwig wrote: > On Tue, May 09, 2023 at 02:52:30PM +0800, Ed Tsai wrote: >> The tags allocation is limited by the fair sharing algorithm. It hurts >> the performance for UFS devices, because the queue depth of general I/O >> is reduced by half once the UFS send a control command. > > But it is there for a reason. You completely fail to explain why you > think your change is safe, and also why you did not try to even explain > where the overhead is and how else you tried to mitigate it. Hi Christoph, For which devices is the fair sharing algorithm useful? As far as I know the legacy block layer did not have an equivalent of the fair sharing algorithm and I'm not aware of any complaints about the legacy block layer regarding to fairness. This is why I proposed in January to remove the fair sharing code entirely. See also https://lore.kernel.org/linux-block/20230103195337.158625-1-bvanassche@acm.org/. Thanks, Bart.