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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 B302BC433FE for ; Fri, 4 Dec 2020 03:12:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7659522517 for ; Fri, 4 Dec 2020 03:12:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727477AbgLDDLy (ORCPT ); Thu, 3 Dec 2020 22:11:54 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:8682 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727407AbgLDDLx (ORCPT ); Thu, 3 Dec 2020 22:11:53 -0500 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4CnHlG3KL7zkkj7; Fri, 4 Dec 2020 11:10:34 +0800 (CST) Received: from [10.136.114.67] (10.136.114.67) by smtp.huawei.com (10.3.19.206) with Microsoft SMTP Server (TLS) id 14.3.487.0; Fri, 4 Dec 2020 11:11:04 +0800 Subject: Re: [f2fs-dev] [PATCH v6] f2fs: compress: support compress level To: Gao Xiang CC: Eric Biggers , , , References: <20201203061715.60447-1-yuchao0@huawei.com> <20201204003119.GA1957051@xiangao.remote.csb> <7b975d1a-a06c-4e14-067e-064afc200934@huawei.com> <20201204020659.GB1963435@xiangao.remote.csb> <3041968d-87d0-d2dc-822b-0bb4a94a365b@huawei.com> <20201204024746.GC1963435@xiangao.remote.csb> From: Chao Yu Message-ID: <15afffcc-636d-b678-0c01-b2fad98d9311@huawei.com> Date: Fri, 4 Dec 2020 11:11:03 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20201204024746.GC1963435@xiangao.remote.csb> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.136.114.67] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/12/4 10:47, Gao Xiang wrote: > On Fri, Dec 04, 2020 at 10:38:08AM +0800, Chao Yu wrote: >> On 2020/12/4 10:06, Gao Xiang wrote: >>> On Fri, Dec 04, 2020 at 09:56:27AM +0800, Chao Yu wrote: > > ... > >> >>> >>> Keep lz4hc dirty data under writeback could block writeback, make kswapd >>> busy, and direct memory reclaim path, I guess that's why rare online >>> compression chooses it. My own premature suggestion is that it'd better >>> to show the CR or performance benefits in advance, and prevent unprivileged >>> users from using high-level lz4hc algorithm (to avoid potential system attack.) >>> either from mount options or ioctl. >> >> Yes, I guess you are worry about destop/server scenario, as for android scenario, >> all compression related flow can be customized, and I don't think we will use >> online lz4hc compress; for other scenario, except the numbers, I need to add the >> risk of using lz4hc algorithm in document. > > Yes, I was saying the general scenario. My overall premature thought is that > before releasing some brand new algorithm, it may be better to evaluate first > it'd benefit to some scenarios first (either on CR or performance side, or > why adding this?), or it would might cause lzo-rle likewise situation in the Yeah, got your point. > future (and add more dependency to algorithms, you might see BWT-based bzip2 > removal patch Oops, is that really allowed? I don't this is a good idea...and I don't see there are deletions from fs/ due to similar reason... Thanks, > https://lore.kernel.org/r/20201117223253.65920-1-alex_y_xu@yahoo.ca > (since I personally don't think BWT is a good algorithm as well)... Just FYI > ... If i'm wrong, kindly ignore me :) > > Thanks, > Gao Xiang > >> >> Thanks, > > . >