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 E39BCCDB474 for ; Fri, 20 Oct 2023 16:17:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229626AbjJTQRU (ORCPT ); Fri, 20 Oct 2023 12:17:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60420 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229630AbjJTQRT (ORCPT ); Fri, 20 Oct 2023 12:17:19 -0400 Received: from mail-pl1-f179.google.com (mail-pl1-f179.google.com [209.85.214.179]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 168E11A4 for ; Fri, 20 Oct 2023 09:17:16 -0700 (PDT) Received: by mail-pl1-f179.google.com with SMTP id d9443c01a7336-1c9e072472bso7531375ad.2 for ; Fri, 20 Oct 2023 09:17:16 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1697818635; x=1698423435; 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=pnUyOVtwtczUA9Fxac+ooOzFfhdkNPufWIH4EAVoJbU=; b=DdthBVyN3BoVu5rjI0Z/2plE7eUPcRYY+XKeNcneyfChwdwQMNT7WBdLsgTRCzhELJ jwnWXLltC92Da/U/dBR5rr97IxvdRCWDsoZ3reHWI2U2YEh/SunvP4iCNFX4v5JU5fRM 75oRfF+yFcGAedg857FZGqC8QegjCJASDmLq8pcOGiqBB8W0kTk9+LN9VTjHljO33gD3 7Gfqrf5sn1KClSqukObcFj45i6owCOnvRHqgBR/pcn/l+W698DKA4Z7SRcIgwcBi5BYV MyYPxXOEglpTm3XjSqnFaXkyhmhtwCDY+JvxpuzGVV0PB2FU2J9vCTf2HFnCTEAR7ydA IqOQ== X-Gm-Message-State: AOJu0YyYlP2ZXgzWpHY4i5Ra/HqYn/686yLCfGyyytU+QwPFLhXMgpmu KJBLzvdQR864dvDz8jqUNC4= X-Google-Smtp-Source: AGHT+IGQbmoTyfS2iMdwvIf2ZqPEYYSHVj8DXCgdodJWR2iqzZLdRSVfl7Nmgxw8gXAUMz3d4kBR6g== X-Received: by 2002:a17:902:eb84:b0:1c3:62c4:7f12 with SMTP id q4-20020a170902eb8400b001c362c47f12mr2770874plg.5.1697818635414; Fri, 20 Oct 2023 09:17:15 -0700 (PDT) Received: from ?IPV6:2601:642:4c08:4945:85f8:4610:95c3:168a? ([2601:642:4c08:4945:85f8:4610:95c3:168a]) by smtp.gmail.com with ESMTPSA id q11-20020a170902dacb00b001c72f51b84asm1707645plx.52.2023.10.20.09.17.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Oct 2023 09:17:14 -0700 (PDT) Message-ID: <0d2dce2a-8e01-45d6-b61b-f76493d55863@acm.org> Date: Fri, 20 Oct 2023 09:17:11 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] block: Improve shared tag set performance Content-Language: en-US To: Christoph Hellwig Cc: Jens Axboe , linux-block@vger.kernel.org, "Martin K . Petersen" , Ming Lei , Keith Busch , Damien Le Moal , Yu Kuai , Ed Tsai References: <20231018180056.2151711-1-bvanassche@acm.org> <20231020044159.GB11984@lst.de> From: Bart Van Assche In-Reply-To: <20231020044159.GB11984@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 10/19/23 21:41, Christoph Hellwig wrote: > On Wed, Oct 18, 2023 at 11:00:56AM -0700, Bart Van Assche wrote: >> Note: it has been attempted to rework this algorithm. See also "[PATCH >> RFC 0/7] blk-mq: improve tag fair sharing" >> (https://lore.kernel.org/linux-block/20230618160738.54385-1-yukuai1@huaweicloud.com/). >> Given the complexity of that patch series, I do not expect that patch >> series to be merged. > > Work is hard, so let's skip it? That's not really the most convincing > argument. Hey, I'm the biggest advocate for code improvement by code > removal, but you better have a really good argument why it doesn't hurt > anyone. Hi Christoph, No, it's not because it's hard to improve the tag fairness algorithm that I'm proposing to skip this work. It's because I'm convinced that an improved fairness algorithm will have a negative performance impact that is larger than that of the current algorithm. Do you agree that the legacy block layer never had any such fairness algorithm and also that nobody ever complained about fairness issues for the legacy block layer? I think that's a strong argument in favor of removing the fairness algorithm. Thanks, Bart.