Re: btrfs mount takes too long time

open_ctree() took 228254398 us. And 98% of it that is 225418272 us
was taken by btrfs_read_block_groups().

-------------------
 1) $ 225418272 us | } /* btrfs_read_block_groups [btrfs] */
 1) * 16934.96 us | btrfs_check_rw_degradable [btrfs]();
 0) 0.967 us | btrfs_apply_pending_changes [btrfs]();
 0) 0.239 us | btrfs_read_qgroup_config [btrfs]();
 0) * 21017.34 us | btrfs_get_root_ref [btrfs]();
 0) + 15.717 us | btrfs_start_pre_rw_mount [btrfs]();
 0) 0.865 us | btrfs_discard_resume [btrfs]();
 0) $ 228254398 us | } /* open_ctree [btrfs] */
-------------------

Now we need to run the same thing on btrfs_read_block_groups(),
could you please run.. [1] (no need of the time).

[1]
  $ umount /btrfs;
  $./ftracegraph btrfs_read_block_groups 3 "*:mod:btrfs" "mount /dev/vg/scratch0 /btrfs"

Thanks, Anand


On 30/08/2021 14:44, Jingyun He wrote:

Hi, Anand,
I have attached the new result.
Kindly check.

Thank you.

On Mon, Aug 30, 2021 at 9:27 AM Anand Jain [off-list ref] wrote:

quoted

Our open_ctree() took around ~223secs (~3.7mins)

   1) $ 223375750 us |  } /* open_ctree [btrfs] */

Unfortunately, the default trace buffer per CPU (4K) wasn't sufficient
and, the trace-buffer rolled over.
So we still don't know how long we spent in btrfs_read_block_groups().
Sorry for my mistake we should go 1 step at a time and, we have to do
this until we narrow it down to a specific function.

Could you please run with the depth = 2 (instead of 3) and use the time
command prefix. Also, pull a new ftracegraph as I have updated it to
display a proper time output.

$ ftracegraph open_ctree 2 "*:mod:btrfs" "time mount /dev/vg/scratch0
/btrfs"

Thanks, Anand

On 29/08/2021 17:42, Jingyun He wrote:

quoted

Hi, Anand

I have attached the file.
Could you kindly check this?

Thank you.

On Sun, Aug 29, 2021 at 7:47 AM Anand Jain [off-list ref] wrote:

quoted

On 28/08/2021 19:58, Jingyun He wrote:

quoted

Hello, all
I'm new to btrfs, I have a HM-SMR 14TB disk, I have formatted it to
btrfs to store the files.

When the device is almost full, it needs about 5 mins to mount the device.

Is it normal? is there any mount option that I can use to reduce the mount time?

    We need to figure out the function taking a longer time (maybe it is
    read-block-groups). I have similar reports on the non zoned device
    as well (with a few TB full of data). But there is no good data yet
    to analyse.

    Could you please collect the trace data from the ftracegraph
    from here [1] (It needs trace-cmd).

    [1] https://github.com/asj/btrfstrace.git

    Run it as in the example below:

    umount /btrfs;

    ./ftracegraph open_ctree 3 "*:mod:btrfs" "mount /dev/vg/scratch0 /btrfs"

    cat /tmp/ftracegraph.out


Thanks, Anand

quoted

Thank you.