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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 A2FACC49ED7 for ; Tue, 17 Sep 2019 03:10:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 736E420678 for ; Tue, 17 Sep 2019 03:10:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=zedlx.com header.i=@zedlx.com header.b="v8IA//Lz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729182AbfIQDKe (ORCPT ); Mon, 16 Sep 2019 23:10:34 -0400 Received: from server53-3.web-hosting.com ([198.54.126.113]:49133 "EHLO server53-3.web-hosting.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728037AbfIQDKe (ORCPT ); Mon, 16 Sep 2019 23:10:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=zedlx.com; s=default; h=MIME-Version:Content-Type:In-Reply-To:References:Subject:Cc:To: From:Message-ID:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=T/auK7Fu9aGEtdosgR+a0REJed466hXBdrsmuK8rqXg=; b=v8IA//LznCjjrX/GBJBEwMN3Vt H/Z9IPGLRsl9gJuQZIP/bNK+PHj8kochY+VKIH7qmK/OytPRRX3oaCWqBLB+vLUUNgp4Xdkd/G5HH KJt540jhqXyg3I8NmC9WEnwhO7Ndfqb53vjcNJaNUDG8fhooCWBkCsVjkByFJCnpUdDglLJv0Ys9A X/OHJbiwP3qjbFyoDdufPrfRUNSTQuaI3qPKaLM0Ph5f+HjzKepLeQjKiSG1sIJuQjduaiR8cPnhr q03oQNTciGXt32ZCXOAjaS/ktlrxLJ+cPWy+Zu/DbkAwuUqkVJqOnwi9FJL5BR2iOhQP4ZGNkP1ob Jme2Xeng==; Received: from [::1] (port=55116 helo=server53.web-hosting.com) by server53.web-hosting.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.92) (envelope-from ) id 1iA3sq-000VYY-RR; Mon, 16 Sep 2019 23:10:33 -0400 Received: from [95.178.242.132] ([95.178.242.132]) by server53.web-hosting.com (Horde Framework) with HTTPS; Mon, 16 Sep 2019 23:10:28 -0400 Date: Mon, 16 Sep 2019 23:10:28 -0400 Message-ID: <20190916231028.Horde.Zo7I8Sj-BWHmmLSDYGUq8nB@server53.web-hosting.com> From: General Zed To: Zygo Blaxell Cc: Chris Murphy , Btrfs BTRFS Subject: Re: Feature requests: online backup - defrag - change RAID level References: <20190912185726.Horde.HMciH9Z16kV4fK10AfUeRA8@server53.web-hosting.com> <20190912235427.GE22121@hungrycats.org> <20190912202604.Horde.2Cvnicewbvpdb39q5eBASP7@server53.web-hosting.com> <20190913031242.GF22121@hungrycats.org> <20190913010552.Horde.cUL303XsYbqREB5g0iiCDKd@server53.web-hosting.com> <20190914005655.GH22121@hungrycats.org> <20190913215038.Horde.gsxNyK9aSRLm6Qsl5sUNhf0@server53.web-hosting.com> <20190914044219.GL22121@hungrycats.org> <20190915135407.Horde.qqs07Bais-BPrjIVxyrrIfo@server53.web-hosting.com> <20190916225126.GB24379@hungrycats.org> In-Reply-To: <20190916225126.GB24379@hungrycats.org> User-Agent: Horde Application Framework 5 Content-Type: text/plain; charset=utf-8; format=flowed; DelSp=Yes MIME-Version: 1.0 Content-Disposition: inline X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - server53.web-hosting.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - zedlx.com X-Get-Message-Sender-Via: server53.web-hosting.com: authenticated_id: zedlryqc/from_h X-Authenticated-Sender: server53.web-hosting.com: general-zed@zedlx.com X-Source: X-Source-Args: X-Source-Dir: X-From-Rewrite: unmodified, already matched Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Quoting Zygo Blaxell : > On Sun, Sep 15, 2019 at 01:54:07PM -0400, General Zed wrote: >> >> Quoting Zygo Blaxell : >> >> > On Fri, Sep 13, 2019 at 09:50:38PM -0400, General Zed wrote: >> > > >> > > Quoting Zygo Blaxell : >> > > >> > > > On Fri, Sep 13, 2019 at 01:05:52AM -0400, General Zed wrote: >> > > > > >> > > > > Quoting Zygo Blaxell : >> > > > > >> > > > > > On Thu, Sep 12, 2019 at 08:26:04PM -0400, General Zed wrote: >> > > > > > > >> > > > > > > Quoting Zygo Blaxell : I have a few questions for you. 1. Does the btrfs driver already keep a cache off all the mentioned trees (entent tree, subvol tree, free space tree, csum tree) in RAM? I guess the answer is YES. This makes defrag easier to implement. 2. Is the size of those caches dynamically configurable? I guess the answer is YES. This makes defrag easier to implement. 3. Can the cache size of csum tree be increased to approx. 128 MB. , for example? I guess the answer is YES. This makes defrag easier to implement. 4. This is a part of format of subvol tree that I don't understand. You said: "A file consists of an inode item followed by extent ref items (aka reflinks) in a subvol tree keyed by (inode, offset) pairs. Subvol tree pages can be shared with other subvol trees to make snapshots." Those "extent ref items" must also be forming a tree. But how are nodes of this tree addressed? The inode&offset is the key, but how do you get an address of a child node? Do nodes in the subvol tree equal the metadata extents? Or is this tree special in that regard? Because, it seems a bit ridiculous to have (for example) a 16 KB metadata extent for each directory or a 16 K metadata extent in the subvol tree for a file that is only a few bytes in length.