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=-8.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2E885C432BE for ; Sat, 28 Aug 2021 00:43:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0899060ED5 for ; Sat, 28 Aug 2021 00:43:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232845AbhH1AoD (ORCPT ); Fri, 27 Aug 2021 20:44:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:58178 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232503AbhH1AoC (ORCPT ); Fri, 27 Aug 2021 20:44:02 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id BEF8860F14; Sat, 28 Aug 2021 00:43:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1630111392; bh=jah1aaOllz3Ob5t19NZqX7ZjZZ2lH5n+1dapisCauwQ=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=GJbKp4uSX/c1BFHuIEAXUZUN78tl/voUlAWWTZpgdsdcmu9+G7WKBORjJyQeVTXJl gGHmAUl7D1oFkAM+XI49Mf09mZX9fnJUOB+UUBpfJ9NF6SI0tbzHXMjw6UyW7vcoTS dk6vxdpV0arO/4o6p86qx+WDbf7jrd+WDvgGBAgVz/3eGzZpmvJGFfQo8AGeB28SxS g5shRAJjfioCS24ASPANj1dhEn4qfBvHcn6NbsjsFKsg1DJS8VIPIAFF5T3Y2VdKjD geOVLxVlj3nu/RVtB1XoskYu92u6Ze4Z0KAEMUljFPVSRdX/ND3YNUuZuemLNCw1yo TrUYHe9Ka861A== Subject: Re: [f2fs-dev] [PATCH v2] f2fs: introduce fragment allocation mode mount option To: Daeho Jeong Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com, Daeho Jeong References: <20210825185747.1627497-1-daeho43@gmail.com> <1f1e6d38-6bd1-17ea-b8ca-a45d1244728f@kernel.org> From: Chao Yu Message-ID: <335d5bb5-7055-c934-33df-a03885382034@kernel.org> Date: Sat, 28 Aug 2021 08:43:11 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/8/27 23:22, Daeho Jeong wrote: >> I'd like to add a fixed chunk/hole fragmentation mode in addition, then >> userspace can control the fragmented chunk/hole with fixed size. >> >> How do you think of renaming "fragment:block" to "fragment:rand_block", and >> then I can add "fragment:fixed_block" option and its logic in addition? >> > > The reason I added the randomness on these values is the segment > selection in SSR mode. > If all the segments have the same free block counts, f2fs will > allocate a new segment sequentially in SSR. I'm fine with this, since test program can customize different fragment degree on segments by setting different chunk/hole size. > This was what I didn't want. Plus, in the real world, the size of hole > and chunk will be different in different segments. > > But, if you think we need this "fragment:fixed_block" mode, I am happy > to have it. :) Thanks a lot. :) As you said it needs to be aligned to real world fragmentation, I notice that: with this way, we can't simulate similar fragment in FTL, due to its page mapping architecture, all fragmented data/node in filesystem will be written sequentially into its blocks. In order to simulate fragment in FTL, we need to: - write data (chunk size) with dummy pages (hole size) to devices - issue discards on those holes I guess fragmenting device (erase blocks) at the same time wouldn't be original intention of this patch, right? Thanks, > >> Do we need to consider multiple thread scenario? in such case, >> .fragment_remained_chunk may update randomly. >> >> In addition, multiple log headers share one .fragment_remained_chunk, >> it may cause unexpected result, it means there may be continuous holes >> or chunks in locality due to swithing between different log headers. >> >> Thanks, >> > > Oh, I overlooked that point. I am going to add the variable for each > segment as you said before. > > Thanks, >