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=-2.5 required=3.0 tests=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 6F448C43219 for ; Thu, 2 May 2019 13:10:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3A98E205C9 for ; Thu, 2 May 2019 13:10:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726363AbfEBNKm (ORCPT ); Thu, 2 May 2019 09:10:42 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:60116 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726203AbfEBNKm (ORCPT ); Thu, 2 May 2019 09:10:42 -0400 Received: from callcc.thunk.org (adsl-173-228-226-134.prtc.net [173.228.226.134]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id x42DAZ2t005938 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 2 May 2019 09:10:37 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id 0E7D9420023; Thu, 2 May 2019 09:10:35 -0400 (EDT) Date: Thu, 2 May 2019 09:10:34 -0400 From: "Theodore Ts'o" To: Amir Goldstein Cc: ezemtsov@google.com, linux-fsdevel , Miklos Szeredi Subject: Re: Initial patches for Incremental FS Message-ID: <20190502131034.GA25007@mit.edu> References: <20190502040331.81196-1-ezemtsov@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, May 02, 2019 at 07:19:52AM -0400, Amir Goldstein wrote: > > This sounds very useful. > > Why does it have to be a new special-purpose Linux virtual file? > Why not FUSE, which is meant for this purpose? > Those are things that you should explain when you are proposing a new > filesystem, > but I will answer for you - because FUSE page fault will incur high > latency also after > blocks are locally available in your backend store. Right? >From the documentation file in the first patch: +Why isn't incremental-fs implemented via FUSE? +---------------------------------------------- +TLDR: FUSE-based filesystems add 20-80% of performance overhead for target +scenarios, and increase power use on mobile beyond acceptable limit +for widespread deployment. A custom kernel filesystem is the way to overcome +these limitations. + There are several paragraphs of more detail which I leave for the interested reader to review.... - Ted