linux-btrfs.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Filipe Manana <fdmanana@kernel.org>
To: "François-Xavier Thomas" <fx.thomas@gmail.com>
Cc: linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: Massive I/O usage from btrfs-cleaner after upgrading to 5.16
Date: Wed, 19 Jan 2022 10:13:53 +0000	[thread overview]
Message-ID: <CAL3q7H7UvBzw998MW1wxxBo+EPCePVikNdG-rT1Zs0Guo71beQ@mail.gmail.com> (raw)
In-Reply-To: <CAEwRaO7LpG+KBYRgB4MGx9td5PO6JvFWpKbyKsHDB=7LKMmAJg@mail.gmail.com>

On Wed, Jan 19, 2022 at 9:44 AM François-Xavier Thomas
<fx.thomas@gmail.com> wrote:
>
> Hi,
>
> More details on graph[0]:
> - First patch (1-byte file) on 5.16.0 did not have a significant impact.
> - Both patches on 5.16.0 did reduce a large part of the I/O but still
> have a high baseline I/O compared to 5.15

So, try with these two more patches on top of that:

https://patchwork.kernel.org/project/linux-btrfs/patch/20220118071904.29991-1-wqu@suse.com/

https://patchwork.kernel.org/project/linux-btrfs/patch/20220118115352.52126-1-wqu@suse.com/

>
> Some people reported that 5.16.1 improved the situation for them, so

I don't see how that's possible, nothing was added to 5.16.1 that
involves defrag.
Might just be a coincidence.

Thanks.

> I'm testing that. It's too early to tell but for now the baseline I/O
> still seems to be high compared to 5.15. Will update with more results
> tomorrow.
>
> François-Xavier
>
> [0] https://i.imgur.com/agzAKGc.png
>
> On Mon, Jan 17, 2022 at 10:37 PM François-Xavier Thomas
> <fx.thomas@gmail.com> wrote:
> >
> > Hi Filipe,
> >
> > Thank you so much for the hints!
> >
> > I compiled 5.16 with the 1-byte file patch and have been running it
> > for a couple of hours now. I/O seems to have been gradually increasing
> > compared to 5.15, but I will wait for tomorrow to have a clearer view
> > on the graphs, then I'll try the both patches.
> >
> > François-Xavier
> >
> > On Mon, Jan 17, 2022 at 5:59 PM Filipe Manana <fdmanana@kernel.org> wrote:
> > >
> > > On Mon, Jan 17, 2022 at 12:02:08PM +0000, Filipe Manana wrote:
> > > > On Mon, Jan 17, 2022 at 11:06:42AM +0100, François-Xavier Thomas wrote:
> > > > > Hello all,
> > > > >
> > > > > Just in case someone is having the same issue: Btrfs (in the
> > > > > btrfs-cleaner process) is taking a large amount of disk IO after
> > > > > upgrading to 5.16 on one of my volumes, and multiple other people seem
> > > > > to be having the same issue, see discussion in [0].
> > > > >
> > > > > [1] is a close-up screenshot of disk I/O history (blue line is write
> > > > > ops, going from a baseline of some 10 ops/s to around 1k ops/s). I
> > > > > downgraded from 5.16 to 5.15 in the middle, which immediately restored
> > > > > previous performance.
> > > > >
> > > > > Common options between affected people are: ssd, autodefrag. No error
> > > > > in the logs, and no other issue aside from performance (the volume
> > > > > works just fine for accessing data).
> > > > >
> > > > > One person reports that SMART stats show a massive amount of blocks
> > > > > being written; unfortunately I do not have historical data for that so
> > > > > I cannot confirm, but this sounds likely given what I see on what
> > > > > should be a relatively new SSD.
> > > > >
> > > > > Any idea of what it could be related to?
> > > >
> > > > There was a big refactor of the defrag code that landed in 5.16.
> > > >
> > > > On a quick glance, when using autodefrag it seems we now can end up in an
> > > > infinite loop by marking the same range for degrag (IO) over and over.
> > > >
> > > > Can you try the following patch? (also at https://pastebin.com/raw/QR27Jv6n)
> > >
> > > Actually try this one instead:
> > >
> > > https://pastebin.com/raw/EbEfk1tF
> > >
> > > Also, there's a bug with defrag running into an (almost) infinite loop when
> > > attempting to defrag a 1 byte file. Someone ran into this and I've just sent
> > > a fix for it:
> > >
> > > https://patchwork.kernel.org/project/linux-btrfs/patch/bcbfce0ff7e21bbfed2484b1457e560edf78020d.1642436805.git.fdmanana@suse.com/
> > >
> > > Maybe that is what you are running into when using autodefrag.
> > > Firt try that fix for the 1 byte file case, and if after that you still run
> > > into problems, then try with the other patch above as well (both patches
> > > applied).
> > >
> > > Thanks.
> > >
> > >
> > >
> > > >
> > > > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> > > > index a5bd6926f7ff..0a9f6125a566 100644
> > > > --- a/fs/btrfs/ioctl.c
> > > > +++ b/fs/btrfs/ioctl.c
> > > > @@ -1213,6 +1213,13 @@ static int defrag_collect_targets(struct btrfs_inode *inode,
> > > >                 if (em->generation < newer_than)
> > > >                         goto next;
> > > >
> > > > +               /*
> > > > +                * Skip extents already under IO, otherwise we can end up in an
> > > > +                * infinite loop when using auto defrag.
> > > > +                */
> > > > +               if (em->generation == (u64)-1)
> > > > +                       goto next;
> > > > +
> > > >                 /*
> > > >                  * For do_compress case, we want to compress all valid file
> > > >                  * extents, thus no @extent_thresh or mergeable check.
> > > >
> > > >
> > > > >
> > > > > François-Xavier
> > > > >
> > > > > [0] https://www.reddit.com/r/btrfs/comments/s4nrzb/massive_performance_degradation_after_upgrading/
> > > > > [1] https://imgur.com/oYhYat1

  reply	other threads:[~2022-01-19 10:14 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-17 10:06 François-Xavier Thomas
2022-01-17 12:02 ` Filipe Manana
2022-01-17 16:59   ` Filipe Manana
2022-01-17 21:37     ` François-Xavier Thomas
2022-01-19  9:44       ` François-Xavier Thomas
2022-01-19 10:13         ` Filipe Manana [this message]
2022-01-20 11:37           ` François-Xavier Thomas
2022-01-20 11:44             ` Filipe Manana
2022-01-20 12:02               ` François-Xavier Thomas
2022-01-20 12:45                 ` Qu Wenruo
2022-01-20 12:55                   ` Filipe Manana
2022-01-20 17:46                 ` Filipe Manana
2022-01-20 18:21                   ` François-Xavier Thomas
2022-01-21 10:49                     ` Filipe Manana
2022-01-21 19:39                       ` François-Xavier Thomas
2022-01-21 23:34                         ` Qu Wenruo
2022-01-22 18:20                           ` François-Xavier Thomas
2022-01-24  7:00                             ` Qu Wenruo
2022-01-25 20:00                               ` François-Xavier Thomas
2022-01-25 23:29                                 ` Qu Wenruo

Reply instructions:

You may reply publicly 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=CAL3q7H7UvBzw998MW1wxxBo+EPCePVikNdG-rT1Zs0Guo71beQ@mail.gmail.com \
    --to=fdmanana@kernel.org \
    --cc=fx.thomas@gmail.com \
    --cc=linux-btrfs@vger.kernel.org \
    --subject='Re: Massive I/O usage from btrfs-cleaner after upgrading to 5.16' \
    /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

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).