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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 97C63C46470 for ; Wed, 8 Aug 2018 06:52:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4464D2170A for ; Wed, 8 Aug 2018 06:52:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="XgwBlrja" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4464D2170A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726823AbeHHJKa (ORCPT ); Wed, 8 Aug 2018 05:10:30 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:44625 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726542AbeHHJKa (ORCPT ); Wed, 8 Aug 2018 05:10:30 -0400 Received: by mail-pg1-f194.google.com with SMTP id r1-v6so611390pgp.11; Tue, 07 Aug 2018 23:52:13 -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:mail-followup-to:references :mime-version:content-disposition:in-reply-to:user-agent; bh=reTqHYG81E8dus0QXhgPXLEntiwrqPYoYtM+tpi7MaY=; b=XgwBlrjaWmCbcOS+pqOzCGpT/xTrq5uwPD6q983Qb3PLsHg1l5gstd0Iact1L1igbD doWGw6MQAowxDoKSsBL57/hl/HpMUcZcrAlAF6aPqw5uHRoTfkrOP4fMy49dBAfivdaT g/oJdhCyHEAma6hiWYtO4OLYDGnsomqapTz0dQlLFeIX4XnKe0BF4EO+g/AbDJbkixz4 0K9vBbYAfBu1VUNPZRu4s6IN9tG8kfup6qTzUHgwgL4yV1GG4J7qEGs9IGTMT9XVAZrk MyXBph8fhDkHNhp97a6PQ021nUUAgvFcGerFiueMA6syV9sTWT+b409li1ae255dUwWy LPZA== 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 :mail-followup-to:references:mime-version:content-disposition :in-reply-to:user-agent; bh=reTqHYG81E8dus0QXhgPXLEntiwrqPYoYtM+tpi7MaY=; b=CZEK4in8JXuvsiAHxLWP524VG1Faur1tkVNf+3ji0aPSWGfj19Ceh+i3cUfEahgcY0 K4FVyDmwoHMnrTNU3k89NFraSNIWLAKfkLh4lmAiIz0qC13ScS9m+QqS9g5rq3TYRTPP rLAvOEELHPtCvgAUi2ROkdHkslELmsAxuh6x68FfiKUVSYkemCqNVDnd+ewDu8zqJFj+ it8EdHJsql2p3MNZNB6TxM9++fZbe1fQqbkDCvVPjMvw/OA4CGMel7S26uUUPpRJu9DS vtb0WJGvbSWUYSOQrc3B+BfNNidp9C+3J6eDsv7PaBKTTBJKNhtSHlF1xluH+ugQ4ZV8 ubNw== X-Gm-Message-State: AOUpUlG6X2h8RE/4Nkz28cVlJyqSaSxBJ+RFhVEryI40WGMrSsb9cIsg liSNEihqr2u5E8saAZxEG4pV6hTiRBAD3g== X-Google-Smtp-Source: AA+uWPyhlYs6ftW5B4cKf8Lt3ntvB+6zlw+QbQ0lJofRVOsCN2vBlcC1Yi0ckdvz/q9Rnvy1ffqxYw== X-Received: by 2002:aa7:87d0:: with SMTP id i16-v6mr1563272pfo.82.1533711133278; Tue, 07 Aug 2018 23:52:13 -0700 (PDT) Received: from linux-zmni.apac.novell.com ([45.122.156.254]) by smtp.gmail.com with ESMTPSA id y63-v6sm5026088pgd.94.2018.08.07.23.52.11 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 07 Aug 2018 23:52:12 -0700 (PDT) Date: Wed, 8 Aug 2018 14:52:05 +0800 From: Sean Fu To: Al Viro Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] fs/buffer.c: Optimize grow_buffer function. Message-ID: <20180808065205.GA21134@linux-zmni.apac.novell.com> Mail-Followup-To: Al Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <1532194217-19002-1-git-send-email-fxinrong@gmail.com> <20180721182116.GC30522@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180721182116.GC30522@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 21, 2018 at 07:21:16PM +0100, Al Viro wrote: > On Sun, Jul 22, 2018 at 01:30:17AM +0800, Sean Fu wrote: > > Use PAGE_SHIFT and i_blkbits of bd_inode directly to avoid ugly sizebits > > calculation. > > Remove ugly sizebits calculation. > > Remove unnecessary sizebits parameter of grow_dev_page. > > > > Reduces code size: > > > > Before: > > > > sean@linux-zmni:~/sda5/source/linus_repo/linux> size fs/buffer.o > > text data bss dec hex filename > > 34037 1510 16 35563 8aeb fs/buffer.o > > > > After: > > > > sean@linux-zmni:~/sda5/source/linus_repo/linux> size fs/buffer.o > > text data bss dec hex filename > > 34021 1510 16 35547 8adb fs/buffer.o > > First of all, 16 bytes is pretty much noise. What's more, the "remove ugly > sizebits calculation" part really needs an explanation of the reasons why > it's safe. You assume that size == 1<bd_inode->i_blkbits; where's > the proof that it always holds? Got it, Thanks This size can be page size(4096) besides block size (1<bd_inode->i_blkbits). I have another question about __getblk_slow function in fs/buffer.c Actually __find_get_block already was invoked before entering __getblk_slow. Can we move __find_get_block after grow_buffers in for loop of __getblk_slow? for (;;) { ... ret = grow_buffers(bdev, block, size, gfp); ... bh = __find_get_block(bdev, block, size); ... }