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From: "Holger Hoffstätte" <holger@applied-asynchrony.com>
To: Qu Wenruo <quwenruo.btrfs@gmx.com>,
	John Ettedgui <john.ettedgui@gmail.com>
Cc: Qu Wenruo <quwenruo@cn.fujitsu.com>,
	Austin S Hemmelgarn <ahferroin7@gmail.com>,
	btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: mount btrfs takes 30 minutes, btrfs check runs out of memory
Date: Tue, 13 Feb 2018 13:26:56 +0100	[thread overview]
Message-ID: <5fc99565-b46a-a52a-b1d4-b3ce3e10c830@applied-asynchrony.com> (raw)
In-Reply-To: <a27b619e-6e39-20e6-413e-c9d5c7a90b6f@gmx.com>


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On 02/13/18 12:40, Qu Wenruo wrote:
>>> The problem is not about how much space it takes, but how many extents
>>> are here in the filesystem.

I have no idea why btrfs' mount even needs to touch all block groups to
get going (which seems to be the root of the problem), but here's a
not so crazy idea for more "mechanical sympathy". Feel free to mock
me if this is terribly wrong or not possible. ;)

Mounting of even large filesystems (with many extents) seems to be fine
on SSDS, but not so fine on rotational storage. We've heard that from
several people with large (multi-TB) filesystems, and obviously it's
even more terrible on 5400RPM drives because their seeks are sooo sloow.

If the problem is that the bgs are touched/iterated in "tree order",
would it then not be possible to sort the block groups in physical order
before trying to load whatever mount needs to load? That way the entire
process would involve less seeking (no backward seeks for one) and the
drive could very likely get more done during a rotation before stepping
further.

cheers,
Holger


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  parent reply	other threads:[~2018-02-13 12:27 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAJ3TwYQXqUZiKhYc5rciTmvGX1RLkHnkQb5SSYAJ7AD+kbudag@mail.gmail.com>
2015-07-31  2:34 ` mount btrfs takes 30 minutes, btrfs check runs out of memory Qu Wenruo
2015-07-31  4:10   ` John Ettedgui
2015-08-02  5:44     ` Georgi Georgiev
     [not found]   ` <CAJ3TwYRN+1tJY+paz=qZT0_XP=r9CcTKbBgX_kZRFOWj8vSK=w@mail.gmail.com>
2015-07-31  4:52     ` Qu Wenruo
     [not found]       ` <CAJ3TwYR5g-JhjmGnZUXqLXc7qV1_=AN5_6sj54JQODbtgG9Aag@mail.gmail.com>
2015-07-31  5:40         ` Qu Wenruo
2015-07-31  5:45           ` John Ettedgui
2015-08-01  4:35             ` John Ettedgui
2015-08-01 10:05               ` Russell Coker
2015-08-04  1:39               ` Qu Wenruo
2015-08-04  1:55                 ` John Ettedgui
2015-08-04  2:31                   ` John Ettedgui
2015-08-04  3:01                   ` Qu Wenruo
2015-08-04  4:58                     ` John Ettedgui
2015-08-04  6:47                       ` Duncan
2015-08-04 11:28                       ` Austin S Hemmelgarn
2015-08-04 17:36                         ` John Ettedgui
2015-08-05 11:30                           ` Austin S Hemmelgarn
2015-08-13 22:38                             ` Vincent Olivier
2015-08-13 23:19                               ` Chris Murphy
2015-08-14  0:30                                 ` Duncan
2015-08-14  2:42                                   ` Vincent Olivier
2015-08-18 17:36                                     ` Vincent Olivier
2015-08-14  2:39                                 ` Vincent Olivier
     [not found]                             ` <CAJ3TwYSW+SvbBrh1u_x+c3HTRx03qSR6BoH5cj_VzCXxZYv6EA@mail.gmail.com>
2016-07-15  3:56                               ` Qu Wenruo
     [not found]                                 ` <CAJ3TwYRXwDVVfT0TRRiM9dEw-7TvY8qG=WvMYKczZOv6wkFWAQ@mail.gmail.com>
2016-07-15  5:24                                   ` Qu Wenruo
2016-07-15  6:56                                     ` Kai Krakow
     [not found]                                     ` <CAJ3TwYSTnQfj=qmBLtnmtXQKexMMD4x=9Gk3p3anf4uF+G26kw@mail.gmail.com>
     [not found]                                       ` <CAJ3TwYTnMPVwkrZEU-=Q_Nq+9Bn0vM3z+EFC8RP=RTyaufSoqw@mail.gmail.com>
2016-07-18  1:13                                         ` Qu Wenruo
     [not found]                                           ` <CAJ3TwYRpc_R-wVur0T6+Uy_aPVXTGpvp_ag1Ar9K2HoB0H1ySQ@mail.gmail.com>
2016-07-18  8:41                                             ` Qu Wenruo
     [not found]                                               ` <CAJ3TwYRH8JVkuv2Hu7FYb+BSwKGrq1spx079zwOF_FO1y=9NFA@mail.gmail.com>
2016-07-18  9:07                                                 ` Qu Wenruo
2016-07-18 15:31                                                   ` Duncan
     [not found]                                                   ` <CAJ3TwYS6UTkWf=PNku3RG7hPrXMKz3yhk2WqCRLix4v_VwgrmA@mail.gmail.com>
2016-07-21  8:10                                                     ` Qu Wenruo
     [not found]                                                       ` <CAJ3TwYQ47SVpbO1Pb-TWjhaTCCpMFFmijwTgmV8=7+1_a6_3Ww@mail.gmail.com>
2016-07-21  8:19                                                         ` Qu Wenruo
2016-07-21 15:47                                                           ` Graham Cobb
2017-04-10  0:52                                                             ` Qu Wenruo
2018-02-13 10:21                                                           ` John Ettedgui
2018-02-13 11:04                                                             ` Qu Wenruo
2018-02-13 11:25                                                               ` John Ettedgui
2018-02-13 11:40                                                                 ` Qu Wenruo
2018-02-13 12:06                                                                   ` John Ettedgui
2018-02-13 12:46                                                                     ` Qu Wenruo
2018-02-13 12:52                                                                       ` John Ettedgui
2018-02-13 12:26                                                                   ` Holger Hoffstätte [this message]
2018-02-13 12:54                                                                     ` Qu Wenruo
2018-02-13 16:24                                                                       ` Holger Hoffstätte
2018-02-14  0:43                                                                         ` Qu Wenruo
2016-07-15 11:29                                 ` Christian Rohmann
2016-07-16 23:53                                   ` Qu Wenruo
2016-07-18 13:42                                     ` Josef Bacik
2016-07-19  0:35                                       ` Qu Wenruo
2016-07-25 13:01                                       ` David Sterba
2016-07-25 13:38                                         ` Josef Bacik
2015-08-04 14:38                     ` Chris Murphy
2015-07-29  5:46 Georgi Georgiev
2015-07-29  6:19 ` Qu Wenruo

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