From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([222.73.24.84]:58688 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751264Ab2E1Igl (ORCPT ); Mon, 28 May 2012 04:36:41 -0400 Message-ID: <4FC33A53.9050607@cn.fujitsu.com> Date: Mon, 28 May 2012 16:41:55 +0800 From: Liu Bo MIME-Version: 1.0 To: WeiFeng Liu CC: linux-btrfs Subject: Re: [RFC PATCH] Decrease Metadata Fragment By Using a Caterpillar Band Method(intro modified) References: <20120528060653.8ABFCE6739@smtp.hushmail.com> In-Reply-To: <20120528060653.8ABFCE6739@smtp.hushmail.com> Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 05/28/2012 02:06 PM, WeiFeng Liu wrote: > On Sunday, May 27, 2012 at 5:44 PM, Liu Bo wrote: > >> Hi, >> >> Thanks for working on this. >> >> Do you have any performance number? >> >> The idea is an interesting one, but I have no idea if it really >> works, because blocks are >> still fragments: >> >> | 16k | 16k | 16k | >> |----|A|----|----|B|----|----|C|----| >> >> >> Or am I missing something? >> >> thanks, >> liubo >> > > Hi, Liu Bo > > I noticed your graphic and what you said, "still fragments" > thanks you. > > According my patch's logic, any COWs for tree block A will be limited in it's > 16k caterpillar band in the example, at least theoretically, and so tree block > B, like the following: > > |<-- A circulated in 16k -->| |<-- B circulated in 16k -->| > |--a-->|--b-->|--c-->|--d-->| |--a-->|--b-->|--c-->|--d-->| > | | | | > |-------------<-------------| |-------------<-------------| > > Liu Bo, are the fragments you mentioned referenced to the ones in a caterpillar > or ones out of a caterpillar? if they are in a caterpillar, nothing would be > worried, because they are supposed to stay there forever, and that efficiency > is just what I want. > Yes, I refer to the space hole between A and B, which may not make readahead happy. But I'm not that sure, anyway, the performance number will tell us the truth :) thanks, liubo > To a certain degree, using a caterpillar for a tree block is somewhat > similar with the way superblock runs, a superblock circularly updated in a > cluster of DISCONTINUOUS blocks within a large range, and I use a caterpillar > band to force a tree block updated circularly in a continuous blocks within a > compact area. > > Sorry, I haven't yet take performance test for my patch now, a bit more times > are still needed for me to check the possible bugs in code's routes before > tests, and any comments are welcome. > > Thanks all you. > > WeiFeng Liu > 523f28f9b3d9c710cacc31dbba644efb1678cf62 > >