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 7EEBDEE3F39 for ; Tue, 12 Sep 2023 22:44:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236785AbjILWoq (ORCPT ); Tue, 12 Sep 2023 18:44:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231491AbjILWop (ORCPT ); Tue, 12 Sep 2023 18:44:45 -0400 Received: from mail-pl1-x629.google.com (mail-pl1-x629.google.com [IPv6:2607:f8b0:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0EA78E4B for ; Tue, 12 Sep 2023 15:44:42 -0700 (PDT) Received: by mail-pl1-x629.google.com with SMTP id d9443c01a7336-1c1e3a4a06fso45521865ad.3 for ; Tue, 12 Sep 2023 15:44:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fromorbit-com.20230601.gappssmtp.com; s=20230601; t=1694558681; x=1695163481; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=ah5Op9UHzow67q6STiy57YfblgAJa0Z+MzvCC70G7KA=; b=jNrYjBG/wjffg70U1TBRnyQx74GjrLWbL9+B4S24Xlc190bNhNUX11uVMIoo2WoMGn RbXYIME3rJfjszbE4zOAPsPoIS0mhSqjDBepBhGyBRj7bzmJ0IV1dR2VNvLAHOlrqly+ TTTegmVLNml1EVQInH+mJ4reT33aG/vthATMp8eDuDCCarE2N3tz+/eSAfDXowu+gYi5 cnB6hdnuz+6Vk2nrbXv/9KsinxVxCZle2d2+ScpPe+8UtovNpmt+3znnhGFr36rizLWQ hXOUw6YVaPUYvHeSoyoBJuuJs1KSXjQBjWMxxAAtNBfNIvYIqewLwmna/y0l2jUi/JPu QtjQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1694558681; x=1695163481; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=ah5Op9UHzow67q6STiy57YfblgAJa0Z+MzvCC70G7KA=; b=eITaon7pFUMOTEgXXGspUkg8BGmiiMNX2igUcuLHn8JgvO6Vnmh9jRv4QBjgopIKkA I20C2M/hQ81p+EsJ2ItdUh//6vkoRsJ0clHW1bR7N9ixjJjYGxix+YPbMUBhwWCCWutA E3n+LXYT9qIrZ9E2fNDtkHHYNtuxXNVCiVbYRsOcsznckJbDJL+TAuXQlfabPwmhcw19 vUwhZki7cgoJcxCGAyQXsDjdiSm2dOmPwXMguGm/SKamKtXfl436wKjm+S3OxqQv0Ozc dTeM0jYeo1OU4kB0dLr2UHqrFQHg3pOqRGCFlLTJThgvgaYwBsTJNRiXcoZ5vjpPFU/a f+zA== X-Gm-Message-State: AOJu0Yx/eC14rA7UTH9AFkOv5WcQvBLVjSJRDjwmOKC4RvMv8lTMw4Pd f6DMOqeNl/hf8MWO9xP4Hg4DC7u4qlZQ9Zqnswc= X-Google-Smtp-Source: AGHT+IHBXmbSUte83WfShO2qynzMF12my3Babt8JezgZzeHlmJ5Kp5tUIevLyDLaZgj1jaa/IH5ZVg== X-Received: by 2002:a17:903:120d:b0:1bb:994c:bc43 with SMTP id l13-20020a170903120d00b001bb994cbc43mr1283734plh.18.1694558681467; Tue, 12 Sep 2023 15:44:41 -0700 (PDT) Received: from dread.disaster.area (pa49-195-66-88.pa.nsw.optusnet.com.au. [49.195.66.88]) by smtp.gmail.com with ESMTPSA id d4-20020a170902c18400b001bba3a4888bsm8957634pld.102.2023.09.12.15.44.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Sep 2023 15:44:40 -0700 (PDT) Received: from dave by dread.disaster.area with local (Exim 4.96) (envelope-from ) id 1qgC7Z-00EPVj-2t; Wed, 13 Sep 2023 08:44:37 +1000 Date: Wed, 13 Sep 2023 08:44:37 +1000 From: Dave Chinner To: Wang Jianchao Cc: djwong@kernel.org, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V2] xfs: use roundup_pow_of_two instead of ffs during xlog_find_tail Message-ID: References: <63b3742c-0efe-c096-c737-a0e0419480bd@outlook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Tue, Sep 12, 2023 at 03:20:56PM +0800, Wang Jianchao wrote: > > In our production environment, we find that mounting a 500M /boot > which is umount cleanly needs ~6s. One cause is that ffs() is > used by xlog_write_log_records() to decide the buffer size. It > can cause a lot of small IO easily when xlog_clear_stale_blocks() > needs to wrap around the end of log area and log head block is > not power of two. Things are similar in xlog_find_verify_cycle(). > > The code is able to handed bigger buffer very well, we can use > roundup_pow_of_two() to replace ffs() directly to avoid small > and sychronous IOs. > > Changes in V1: > - Also replace the ffs in xlog_find_verify_cycle() Change logs go either below the --- line or in the cover letter, not the commit itself. Other than that, the change looks ok. The use of ffs() was added in 2002 simply to make buffers a power-of-2 size. I don't think it had anything to do with trying to maximise the actual buffer size at all, otherwise it would have made to use fls() like roundup_pow_of_two() does... Reviewed-by: Dave Chinner -- Dave Chinner david@fromorbit.com