Linux-BTRFS Archive on lore.kernel.org
 help / color / Atom feed
From: General Zed <general-zed@zedlx.com>
To: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Cc: Chris Murphy <lists@colorremedies.com>,
	Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: Feature requests: online backup - defrag - change RAID level
Date: Tue, 17 Sep 2019 00:05:06 -0400
Message-ID: <20190917000506.Horde.IwnY98o2FCxGuJVRhmMVBAp@server53.web-hosting.com> (raw)
In-Reply-To: <20190916231028.Horde.Zo7I8Sj-BWHmmLSDYGUq8nB@server53.web-hosting.com>


Quoting General Zed <general-zed@zedlx.com>:

> Quoting Zygo Blaxell <ce3g8jdj@umail.furryterror.org>:
>
>> On Sun, Sep 15, 2019 at 01:54:07PM -0400, General Zed wrote:
>>>
>>> Quoting Zygo Blaxell <ce3g8jdj@umail.furryterror.org>:
>>>
>>>> On Fri, Sep 13, 2019 at 09:50:38PM -0400, General Zed wrote:
>>>> >
>>>> > Quoting Zygo Blaxell <ce3g8jdj@umail.furryterror.org>:
>>>> >
>>>> > > On Fri, Sep 13, 2019 at 01:05:52AM -0400, General Zed wrote:
>>>> > > >
>>>> > > > Quoting Zygo Blaxell <ce3g8jdj@umail.furryterror.org>:
>>>> > > >
>>>> > > > > On Thu, Sep 12, 2019 at 08:26:04PM -0400, General Zed wrote:
>>>> > > > > >
>>>> > > > > > Quoting Zygo Blaxell <ce3g8jdj@umail.furryterror.org>:
>
> 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.

Oh, I think I get the answer to 4.

There can be multiple directory items per metadata extent and multiple  
inode items per metadata extent. Bu t they all have the same parent.  
So a file will just have an inode item, but this inode item will not  
occupy the entire metadata extent. Also, there could be some smart  
optimizations there so that the inode reflinks-to-file-extents are  
pack together with inode header.

That means there are no stale entries in any metadata extents. There  
are only stale metadata extents i.e. unused metadata extents. But,  
they would be enumerated in the free extents tree, right? Did I get  
that right?



  reply index

Thread overview: 111+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09  2:55 zedlryqc
2019-09-09  3:51 ` Qu Wenruo
2019-09-09 11:25   ` zedlryqc
2019-09-09 12:18     ` Qu Wenruo
2019-09-09 12:28       ` Qu Wenruo
2019-09-09 17:11         ` webmaster
2019-09-10 17:39           ` Andrei Borzenkov
2019-09-10 22:41             ` webmaster
2019-09-09 15:29       ` Graham Cobb
2019-09-09 17:24         ` Remi Gauvin
2019-09-09 19:26         ` webmaster
2019-09-10 19:22           ` Austin S. Hemmelgarn
2019-09-10 23:32             ` webmaster
2019-09-11 12:02               ` Austin S. Hemmelgarn
2019-09-11 16:26                 ` Zygo Blaxell
2019-09-11 17:20                 ` webmaster
2019-09-11 18:19                   ` Austin S. Hemmelgarn
2019-09-11 20:01                     ` webmaster
2019-09-11 21:42                       ` Zygo Blaxell
2019-09-13  1:33                         ` General Zed
2019-09-11 21:37                     ` webmaster
2019-09-12 11:31                       ` Austin S. Hemmelgarn
2019-09-12 19:18                         ` webmaster
2019-09-12 19:44                           ` Chris Murphy
2019-09-12 21:34                             ` General Zed
2019-09-12 22:28                               ` Chris Murphy
2019-09-12 22:57                                 ` General Zed
2019-09-12 23:54                                   ` Zygo Blaxell
2019-09-13  0:26                                     ` General Zed
2019-09-13  3:12                                       ` Zygo Blaxell
2019-09-13  5:05                                         ` General Zed
2019-09-14  0:56                                           ` Zygo Blaxell
2019-09-14  1:50                                             ` General Zed
2019-09-14  4:42                                               ` Zygo Blaxell
2019-09-14  4:53                                                 ` Zygo Blaxell
2019-09-15 17:54                                                 ` General Zed
2019-09-16 22:51                                                   ` Zygo Blaxell
2019-09-17  1:03                                                     ` General Zed
2019-09-17  1:34                                                       ` General Zed
2019-09-17  1:44                                                       ` Chris Murphy
2019-09-17  4:55                                                         ` Zygo Blaxell
2019-09-17  4:19                                                       ` Zygo Blaxell
2019-09-17  3:10                                                     ` General Zed
2019-09-17  4:05                                                       ` General Zed [this message]
2019-09-14  1:56                                             ` General Zed
2019-09-13  5:22                                         ` General Zed
2019-09-13  6:16                                         ` General Zed
2019-09-13  6:58                                         ` General Zed
2019-09-13  9:25                                           ` General Zed
2019-09-13 17:02                                             ` General Zed
2019-09-14  0:59                                             ` Zygo Blaxell
2019-09-14  1:28                                               ` General Zed
2019-09-14  4:28                                                 ` Zygo Blaxell
2019-09-15 18:05                                                   ` General Zed
2019-09-16 23:05                                                     ` Zygo Blaxell
2019-09-13  7:51                                         ` General Zed
2019-09-13 11:04                                     ` Austin S. Hemmelgarn
2019-09-13 20:43                                       ` Zygo Blaxell
2019-09-14  0:20                                         ` General Zed
2019-09-14 18:29                                       ` Chris Murphy
2019-09-14 23:39                                         ` Zygo Blaxell
2019-09-13 11:09                                   ` Austin S. Hemmelgarn
2019-09-13 17:20                                     ` General Zed
2019-09-13 18:20                                       ` General Zed
2019-09-12 19:54                           ` Austin S. Hemmelgarn
2019-09-12 22:21                             ` General Zed
2019-09-13 11:53                               ` Austin S. Hemmelgarn
2019-09-13 16:54                                 ` General Zed
2019-09-13 18:29                                   ` Austin S. Hemmelgarn
2019-09-13 19:40                                     ` General Zed
2019-09-14 15:10                                       ` Jukka Larja
2019-09-12 22:47                             ` General Zed
2019-09-11 21:37                   ` Zygo Blaxell
2019-09-11 23:21                     ` webmaster
2019-09-12  0:10                       ` Remi Gauvin
2019-09-12  3:05                         ` webmaster
2019-09-12  3:30                           ` Remi Gauvin
2019-09-12  3:33                             ` Remi Gauvin
2019-09-12  5:19                       ` Zygo Blaxell
2019-09-12 21:23                         ` General Zed
2019-09-14  4:12                           ` Zygo Blaxell
2019-09-16 11:42                             ` General Zed
2019-09-17  0:49                               ` Zygo Blaxell
2019-09-17  2:30                                 ` General Zed
2019-09-17  5:30                                   ` Zygo Blaxell
2019-09-17 10:07                                     ` General Zed
2019-09-17 23:40                                       ` Zygo Blaxell
2019-09-18  4:37                                         ` General Zed
2019-09-18 18:00                                           ` Zygo Blaxell
2019-09-10 23:58             ` webmaster
2019-09-09 23:24         ` Qu Wenruo
2019-09-09 23:25         ` webmaster
2019-09-09 16:38       ` webmaster
2019-09-09 23:44         ` Qu Wenruo
2019-09-10  0:00           ` Chris Murphy
2019-09-10  0:51             ` Qu Wenruo
2019-09-10  0:06           ` webmaster
2019-09-10  0:48             ` Qu Wenruo
2019-09-10  1:24               ` webmaster
2019-09-10  1:48                 ` Qu Wenruo
2019-09-10  3:32                   ` webmaster
2019-09-10 14:14                     ` Nikolay Borisov
2019-09-10 22:35                       ` webmaster
2019-09-11  6:40                         ` Nikolay Borisov
2019-09-10 22:48                     ` webmaster
2019-09-10 23:14                   ` webmaster
2019-09-11  0:26               ` webmaster
2019-09-11  0:36                 ` webmaster
2019-09-11  1:00                 ` webmaster
2019-09-10 11:12     ` Austin S. Hemmelgarn
2019-09-09  3:12 webmaster

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190917000506.Horde.IwnY98o2FCxGuJVRhmMVBAp@server53.web-hosting.com \
    --to=general-zed@zedlx.com \
    --cc=ce3g8jdj@umail.furryterror.org \
    --cc=linux-btrfs@vger.kernel.org \
    --cc=lists@colorremedies.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-BTRFS Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-btrfs/0 linux-btrfs/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-btrfs linux-btrfs/ https://lore.kernel.org/linux-btrfs \
		linux-btrfs@vger.kernel.org
	public-inbox-index linux-btrfs

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-btrfs


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git