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=-4.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 75DFFC6369E for ; Wed, 2 Dec 2020 20:34:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 22EB4221FA for ; Wed, 2 Dec 2020 20:34:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729954AbgLBUdb (ORCPT ); Wed, 2 Dec 2020 15:33:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42948 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729176AbgLBUd2 (ORCPT ); Wed, 2 Dec 2020 15:33:28 -0500 Received: from mail-qv1-xf44.google.com (mail-qv1-xf44.google.com [IPv6:2607:f8b0:4864:20::f44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7245FC0617A7; Wed, 2 Dec 2020 12:32:42 -0800 (PST) Received: by mail-qv1-xf44.google.com with SMTP id k3so1377105qvz.4; Wed, 02 Dec 2020 12:32:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=bi4yjCY3FALmEA0HGC/jzq/xV0+n6rZC92KaCyBy7YM=; b=R9hr6FKWwwTYwc20K91Z1UWrBTBrsMw0yhziMzEDLFh0MDE++f1Zxe7twY7/Ywqh2W 54jGKU1/mXkXPShm/fltc4fFO0gVC93iGuiRPTWbWyLcjV2DLyIWwcwF1iWXfjJ65UY5 1gKVaVBB4f5PycgJvJUvoxJ2/mHpL0dYwhopf5QV72CwaBgqWFwrhHvVym/Vnp+RHda9 trdwWObES7APrwV42cIoHrS0wl4uLoKGfCi4ykpSByrqINfBXQjJ4DnGql1ChuzlvgZz oYg33QQFC4Tu0+rpnznQl7wUBPcvwvR3hxNcKGZhZiwZq6gjJtgjuD7CGSBONc4+SGHK 4Vxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=bi4yjCY3FALmEA0HGC/jzq/xV0+n6rZC92KaCyBy7YM=; b=d/qEgLmHGwUu2Z3MKCLt7i3EkMDKByhSILs1UwlXqiaVZTH6luHkIeUATKY7lEAuMj p43Qw3M79E7JW1Vx/NJyxJ2udm0GSDNy69xAPllx543XJkXm9ZF5yopGyPojrVu2iuCB XeEpgV2VL+jbWU2nbHi1Tz3GwfHn/+7vsVDlYLI11lnlRYoAWZWUUfGX1mIuLzePdBjE LI6CL0SWZmdf2dwilQ6M4cKpaKQmT7qHyuj0MSuGNPxJ6zUAmr33HzKcE1atlSHuUygM DLQGTe5co59u7lLVyz3HivxmHXC1dlw706QHVAXsOufrnUiC+iImOeHGXML7uUL0UEvs MRcQ== X-Gm-Message-State: AOAM530rzCY7ul+UcNwrw1YyqDitRye+qMHyssRMyO5F8w9R/lP/l4vB S/79e7UAE/UHq6Y4JGeN+IAchbFktboYlw== X-Google-Smtp-Source: ABdhPJxOKYIsdGtRADGmB5ndMCWZLHbqy637TkYN0i1VVXW8GFv7NEfdvJQ4DtiXKCsS6MEMmgMhnw== X-Received: by 2002:ad4:4673:: with SMTP id z19mr4532382qvv.60.1606941161611; Wed, 02 Dec 2020 12:32:41 -0800 (PST) Received: from localhost ([2620:10d:c091:480::1:8dbd]) by smtp.gmail.com with ESMTPSA id p62sm3063465qkf.50.2020.12.02.12.32.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Dec 2020 12:32:40 -0800 (PST) Sender: Tejun Heo Date: Wed, 2 Dec 2020 15:32:13 -0500 From: Tejun Heo To: Baolin Wang Cc: axboe@kernel.dk, baolin.wang7@gmail.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] blk-iocost: Optimize the ioc_refreash_vrate() function Message-ID: References: <071dbbbdfecaebf9e850e622c52dd591969e21ab.1606617087.git.baolin.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <071dbbbdfecaebf9e850e622c52dd591969e21ab.1606617087.git.baolin.wang@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 29, 2020 at 10:37:18AM +0800, Baolin Wang wrote: > The ioc_refreash_vrate() will only be called in ioc_timer_fn() after > starting a new period or stopping the period. > > So when starting a new period, the variable 'pleft' in ioc_refreash_vrate() > is always the period's time, which means if the abs(ioc->vtime_err) > is less than the period's time, the vcomp is 0, and we do not need > compensate the vtime_rate in this case, just set it as the base vrate > and return. > > When stopping the period, the ioc->vtime_err will be cleared to 0, > and we also do not need to compensate the vtime_rate, just set it as > the base vrate and return. Before, the function did something which is conceptually discrete and describable. After, its operation is intertwined with when it's called. I don't think this sort of micro optimizations are beneficial in cold paths. Thanks. -- tejun