Re: extremely slow writes to array [now not degraded]

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Now the missing disk was added and recovered so we have a fully redundant raid6. System was restarted now.

I copied the same tree as before and the system has so far spent 2 hour slowly writing the dirty blocks.

Can I have someone (an expert) suggest why w_await is so high (seconds)?

13:56:08 Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
13:56:08 md127            0.00      0.00     0.00   0.00    0.00     0.00    2.40     17.60     0.00   0.00 1473.96     7.33    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    3.54   3.97
13:56:08 sdb              0.00      0.00     0.00   0.00    0.00     0.00    1.40     15.80     3.10  68.89    2.00    11.29    0.00      0.00     0.00   0.00    0.00     0.00    1.20    1.92    0.01   0.39
13:56:08 sdc              0.00      0.00     0.00   0.00    0.00     0.00    1.40     15.80     3.10  68.89    2.57    11.29    0.00      0.00     0.00   0.00    0.00     0.00    1.20    2.50    0.01   0.47
13:56:08 sdd              0.00      0.00     0.00   0.00    0.00     0.00    1.20      2.60     0.00   0.00    2.75     2.17    0.00      0.00     0.00   0.00    0.00     0.00    1.20    2.42    0.01   0.43
13:56:08 sde              0.20      2.00     0.30  60.00    0.50    10.00    1.60      7.00     0.70  30.43   14.38     4.38    0.00      0.00     0.00   0.00    0.00     0.00    1.20    2.83    0.03   2.22
13:56:08 sdf              0.20      2.00     0.30  60.00    0.00    10.00    1.60      7.00     0.70  30.43   14.06     4.38    0.00      0.00     0.00   0.00    0.00     0.00    1.20    3.08    0.03   2.19
13:56:08 sdg              0.40     15.20     3.40  89.47    4.50    38.00    1.60     17.80     3.40  68.00   15.94    11.12    0.00      0.00     0.00   0.00    0.00     0.00    1.20    3.17    0.03   2.19
13:56:08 sdh              0.20      2.40     0.40  66.67    0.00    12.00    1.40      5.00     0.40  22.22   14.07     3.57    0.00      0.00     0.00   0.00    0.00     0.00    1.20    1.67    0.02   1.94
13:56:18 md127            0.00      0.00     0.00   0.00    0.00     0.00    0.60      2.40     0.00   0.00   19.67     4.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.01  10.29
13:56:18 sdb              0.00      0.00     0.00   0.00    0.00     0.00    0.20      0.40     0.00   0.00    0.00     2.00    0.00      0.00     0.00   0.00    0.00     0.00    0.20    0.00    0.00   0.03
13:56:18 sdc              0.00      0.00     0.00   0.00    0.00     0.00    0.20      0.40     0.00   0.00    0.50     2.00    0.00      0.00     0.00   0.00    0.00     0.00    0.20    0.50    0.00   0.03
13:56:18 sdd              0.00      0.00     0.00   0.00    0.00     0.00    0.20      0.40     0.00   0.00    0.50     2.00    0.00      0.00     0.00   0.00    0.00     0.00    0.20    0.50    0.00   0.03
13:56:18 sde              0.00      0.00     0.00   0.00    0.00     0.00    0.40      2.80     0.40  50.00    9.25     7.00    0.00      0.00     0.00   0.00    0.00     0.00    0.20    9.00    0.01   0.39
13:56:18 sdf              0.00      0.00     0.00   0.00    0.00     0.00    0.40      2.80     0.40  50.00   13.00     7.00    0.00      0.00     0.00   0.00    0.00     0.00    0.20    9.50    0.01   0.54
13:56:18 sdg              0.00      0.00     0.00   0.00    0.00     0.00    0.20      0.40     0.00   0.00    9.00     2.00    0.00      0.00     0.00   0.00    0.00     0.00    0.20    0.50    0.00   0.20
13:56:18 sdh              0.20      2.40     0.40  66.67   11.50    12.00    0.40      2.80     0.40  50.00    9.25     7.00    0.00      0.00     0.00   0.00    0.00     0.00    0.20    4.50    0.01   0.62
13:56:28 md127            0.00      0.00     0.00   0.00    0.00     0.00    2.90     22.40     0.00   0.00 2791.14     7.72    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    8.09  12.99
13:56:28 sdb              0.00      0.00     0.00   0.00    0.00     0.00    1.50     20.20     4.10  73.21    4.20    13.47    0.00      0.00     0.00   0.00    0.00     0.00    1.10    5.27    0.01   0.71
13:56:28 sdc              0.00      0.00     0.00   0.00    0.00     0.00    1.50     20.20     4.10  73.21    5.00    13.47    0.00      0.00     0.00   0.00    0.00     0.00    1.10    6.00    0.01   0.64
13:56:28 sdd              0.00      0.00     0.00   0.00    0.00     0.00    1.10      2.20     0.00   0.00    0.73     2.00    0.00      0.00     0.00   0.00    0.00     0.00    1.10    0.55    0.00   0.18
13:56:28 sde              0.00      0.00     0.00   0.00    0.00     0.00    1.50      6.60     0.70  31.82   16.20     4.40    0.00      0.00     0.00   0.00    0.00     0.00    1.10    2.55    0.03   2.56
13:56:28 sdf              0.00      0.00     0.00   0.00    0.00     0.00    1.50      6.60     0.70  31.82   14.00     4.40    0.00      0.00     0.00   0.00    0.00     0.00    1.10    5.09    0.03   2.19
13:56:28 sdg              0.10      0.40     0.00   0.00    0.00     4.00    1.20      2.60     0.00   0.00   15.50     2.17    0.00      0.00     0.00   0.00    0.00     0.00    1.10    2.27    0.02   1.95
13:56:28 sdh              0.70     22.00     4.80  87.27    2.43    31.43    1.80     24.20     4.80  72.73   12.28    13.44    0.00      0.00     0.00   0.00    0.00     0.00    1.10    5.36    0.03   2.19

TIA

On 06/11/2023 10.06, eyal@xxxxxxxxxxxxxx wrote:

This is a more organized summary of a number of recent threads I posted about this problem.
The last one is titled "problem with recovered array".


The environment
===============

Fedora 28

$ uname -a
Linux e7.eyal.emu.id.au 6.5.8-200.fc38.x86_64 #1 SMP PREEMPT_DYNAMIC Fri Oct 20 15:53:48 UTC 2023 x86_64 GNU/Linux

7 disks raid6 array(*1). boot, root and swap on a separate SSD.

$ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md127 : active raid6 sde1[4] sdc1[9] sdf1[5] sdb1[8] sdd1[7] sdg1[6]
       58593761280 blocks super 1.2 level 6, 512k chunk, algorithm 2 [7/6] [_UUUUUU]
       bitmap: 88/88 pages [352KB], 65536KB chunk

One disk was removed recently and sent for replacement. The system felt OK but a few days later I noticed an issue...

The problem
===========

I wanted to copy data from a SATA drive (/data2) into the array (/data1):

I started copying the full dataset (260GB 8,911k files). rsync soon stopped with 100%CPU. It was killed.
4GB (system limit) dirty blocks were created, which took 12h to clear.

I later used a smaller, partial dataset.

$ sudo find /data2/no-backup/old-backups/tapes/01/file.14.data | wc -l
5380

$ sudo du -sm /data2/no-backup/old-backups/tapes/01/file.14.data
93      /data2/no-backup/old-backups/tapes/01/file.14.data

$ sudo rsync -aHSK --stats --progress --checksum-choice=none --no-compress -W /data2/no-backup/old-backups/tapes/01/file.14.data /data1/no-backup/old-backups/
     In this small test rsync completed quickly.

The copy completed fast but the kthread took about 1.5 hours at 100%CPU  to clear the dirty blocks.
- When copying more files (3-5GB) the rsync was consuming 100%CPU and started pausing every few files (then killed).
- The same copy to a plain (non array) disk completes quickly, no issues.
- A 'dd if=/dev/zero of=/data1/no-backup/old-backups/100GB' completed quickly, no issues.
- during a test a mythtv recording was going which DID NOT add to the dirty blocks but wrote to disk quickly.

I observed a kthread flush thread running at 100%CPU

     PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
  944760 root      20   0       0      0      0 R 100.0   0.0 164:00.85 kworker/u16:3+flush-9:127

rsync was killed but the kthread remained. Copying less data had rsync complete but the kthread still stayed up for over an hour.

The system became sluggish, even typing into vi had pauses.
See also (*7) for a side issue.

While the dirty blocks are slowly clearing, at some point it resolves in a burst.
Another test started with 1.6GB dirty blocks and resolved 12h later at 116MB.
In a controlled (short) test it started with 260MB and resolved 80m later at 40MB.
Then another (short) test started with 2.4GB and resolved in 90m at around 1GB.

I cannot see the pattern but clearly the array CAN sustain a high rate of writing, and maybe it is not the array
that is holding back the flush kthread?

I ran iostat which showed very few writes to the array(*2).

I also ran iostat on the member devices (*3), same low rate.

You can see how the %util of the array is often high (13.86) while the members are in the low single digits. One example:

          Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
15:35:52 md127            0.80      3.20     0.00   0.00   13.75     4.00   43.60   1419.60     0.00   0.00   99.34    32.56    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    4.34  13.86
15:35:52 sdb              0.60     85.20    20.70  97.18   14.33   142.00    2.70    470.15   115.20  97.71    2.07   174.13    0.00      0.00     0.00   0.00    0.00     0.00    0.80    4.25    0.02   1.25
15:35:52 sdc              1.20     97.20    23.10  95.06   10.50    81.00    2.20    371.75    91.10  97.64    2.59   168.98    0.00      0.00     0.00   0.00    0.00     0.00    0.80    2.12    0.02   1.13
15:35:52 sdd              2.10    305.60    74.30  97.25   14.62   145.52    1.70    234.95    57.40  97.12    7.71   138.21    0.00      0.00     0.00   0.00    0.00     0.00    0.80    1.12    0.04   2.43
15:35:52 sde              1.50    288.40    70.60  97.92   17.47   192.27    1.90    278.95    68.20  97.29    9.74   146.82    0.00      0.00     0.00   0.00    0.00     0.00    0.80    0.38    0.05   2.60
15:35:52 sdf              1.30    334.00    82.20  98.44   26.31   256.92    2.30    351.35    85.90  97.39    7.74   152.76    0.00      0.00     0.00   0.00    0.00     0.00    0.80    2.00    0.05   2.34
15:35:52 sdg              0.80    215.20    53.00  98.51   18.38   269.00    2.90    510.55   125.10  97.73    7.03   176.05    0.00      0.00     0.00   0.00    0.00     0.00    0.80    3.75    0.04   2.53

Advice from the list suggested I follow some meminfo numbers (Dirty, Buffers, MemFree)(*4).

I was also asked to run 'perf top' (*5).

Also a few sysrq 'w' and 'l' were used to try to see if anything is visible(6).
I ran sysrq 't' (twice) and kept the huge log.

[BTW, I have the full logs saved in case they are needed].

If necessary, I can trigger the problem easily, if more data is required.

The opinion I received suggests that there may be a kernel problem. another poster has the same issue.

TIA

(*1)
$ sudo mdadm -D /dev/md127
/dev/md127:
            Version : 1.2
      Creation Time : Fri Oct 26 17:24:59 2018
         Raid Level : raid6
         Array Size : 58593761280 (54.57 TiB 60.00 TB)
      Used Dev Size : 11718752256 (10.91 TiB 12.00 TB)
       Raid Devices : 7
      Total Devices : 6
        Persistence : Superblock is persistent

      Intent Bitmap : Internal

        Update Time : Sun Nov  5 18:15:07 2023
              State : clean, degraded
     Active Devices : 6
    Working Devices : 6
     Failed Devices : 0
      Spare Devices : 0

             Layout : left-symmetric
         Chunk Size : 512K

Consistency Policy : bitmap

               Name : e4.eyal.emu.id.au:127
               UUID : 15d250cf:fe43eafb:5779f3d8:7e79affc
             Events : 5017887

     Number   Major   Minor   RaidDevice State
        -       0        0        0      removed
        8       8       17        1      active sync   /dev/sdb1
        9       8       33        2      active sync   /dev/sdc1
        7       8       49        3      active sync   /dev/sdd1
        4       8       65        4      active sync   /dev/sde1
        5       8       81        5      active sync   /dev/sdf1
        6       8       97        6      active sync   /dev/sdg1

$ sudo mdadm -E /dev/sd{b,c,d,e,f,g}1

/dev/sdb1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x1
      Array UUID : 15d250cf:fe43eafb:5779f3d8:7e79affc
            Name : e4.eyal.emu.id.au:127
   Creation Time : Fri Oct 26 17:24:59 2018
      Raid Level : raid6
    Raid Devices : 7

  Avail Dev Size : 23437504512 sectors (10.91 TiB 12.00 TB)
      Array Size : 58593761280 KiB (54.57 TiB 60.00 TB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
    Unused Space : before=262064 sectors, after=0 sectors
           State : clean
     Device UUID : 4bfcc6d6:165b6a78:b8fad560:51ff21de

Internal Bitmap : 8 sectors from superblock
     Update Time : Sun Nov  5 05:09:23 2023
   Bad Block Log : 512 entries available at offset 56 sectors
        Checksum : d915eee6 - correct
          Events : 5014067

          Layout : left-symmetric
      Chunk Size : 512K

    Device Role : Active device 1
    Array State : .AAAAAA ('A' == active, '.' == missing, 'R' == replacing)

/dev/sdc1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x1
      Array UUID : 15d250cf:fe43eafb:5779f3d8:7e79affc
            Name : e4.eyal.emu.id.au:127
   Creation Time : Fri Oct 26 17:24:59 2018
      Raid Level : raid6
    Raid Devices : 7

  Avail Dev Size : 23437504512 sectors (10.91 TiB 12.00 TB)
      Array Size : 58593761280 KiB (54.57 TiB 60.00 TB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
    Unused Space : before=262064 sectors, after=0 sectors
           State : clean
     Device UUID : 7fb0b851:c3d0463b:6460ff66:170088b9

Internal Bitmap : 8 sectors from superblock
     Update Time : Sun Nov  5 05:09:23 2023
   Bad Block Log : 512 entries available at offset 56 sectors
        Checksum : f8737f39 - correct
          Events : 5014067

          Layout : left-symmetric
      Chunk Size : 512K

    Device Role : Active device 2
    Array State : .AAAAAA ('A' == active, '.' == missing, 'R' == replacing)

/dev/sdd1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x1
      Array UUID : 15d250cf:fe43eafb:5779f3d8:7e79affc
            Name : e4.eyal.emu.id.au:127
   Creation Time : Fri Oct 26 17:24:59 2018
      Raid Level : raid6
    Raid Devices : 7

  Avail Dev Size : 23437504512 sectors (10.91 TiB 12.00 TB)
      Array Size : 58593761280 KiB (54.57 TiB 60.00 TB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
    Unused Space : before=262064 sectors, after=0 sectors
           State : clean
     Device UUID : ce5bd1bc:3e5c3054:658888dd:9038e09f

Internal Bitmap : 8 sectors from superblock
     Update Time : Sun Nov  5 05:09:23 2023
   Bad Block Log : 512 entries available at offset 56 sectors
        Checksum : d957167c - correct
          Events : 5014067

          Layout : left-symmetric
      Chunk Size : 512K

    Device Role : Active device 3
    Array State : .AAAAAA ('A' == active, '.' == missing, 'R' == replacing)
/dev/sde1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x1
      Array UUID : 15d250cf:fe43eafb:5779f3d8:7e79affc
            Name : e4.eyal.emu.id.au:127
   Creation Time : Fri Oct 26 17:24:59 2018
      Raid Level : raid6
    Raid Devices : 7

  Avail Dev Size : 23437504512 sectors (10.91 TiB 12.00 TB)
      Array Size : 58593761280 KiB (54.57 TiB 60.00 TB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
    Unused Space : before=262064 sectors, after=0 sectors
           State : clean
     Device UUID : 4706a5ab:e7cea085:9af96e3a:81ac89b1

Internal Bitmap : 8 sectors from superblock
     Update Time : Sun Nov  5 05:09:23 2023
   Bad Block Log : 512 entries available at offset 56 sectors
        Checksum : 682b18c1 - correct
          Events : 5014067

          Layout : left-symmetric
      Chunk Size : 512K

    Device Role : Active device 4
    Array State : .AAAAAA ('A' == active, '.' == missing, 'R' == replacing)

/dev/sdf1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x1
      Array UUID : 15d250cf:fe43eafb:5779f3d8:7e79affc
            Name : e4.eyal.emu.id.au:127
   Creation Time : Fri Oct 26 17:24:59 2018
      Raid Level : raid6
    Raid Devices : 7

  Avail Dev Size : 23437504512 sectors (10.91 TiB 12.00 TB)
      Array Size : 58593761280 KiB (54.57 TiB 60.00 TB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
    Unused Space : before=262064 sectors, after=0 sectors
           State : clean
     Device UUID : b1732c74:a34e121d:8347018e:c42b5085

Internal Bitmap : 8 sectors from superblock
     Update Time : Sun Nov  5 05:09:23 2023
   Bad Block Log : 512 entries available at offset 56 sectors
        Checksum : ef7cd313 - correct
          Events : 5014067

          Layout : left-symmetric
      Chunk Size : 512K

    Device Role : Active device 5
    Array State : .AAAAAA ('A' == active, '.' == missing, 'R' == replacing)

/dev/sdg1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x1
      Array UUID : 15d250cf:fe43eafb:5779f3d8:7e79affc
            Name : e4.eyal.emu.id.au:127
   Creation Time : Fri Oct 26 17:24:59 2018
      Raid Level : raid6
    Raid Devices : 7

  Avail Dev Size : 23437504512 sectors (10.91 TiB 12.00 TB)
      Array Size : 58593761280 KiB (54.57 TiB 60.00 TB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
    Unused Space : before=262064 sectors, after=0 sectors
           State : clean
     Device UUID : b44b1807:ed20c6f9:ec0436d7:744d144a

Internal Bitmap : 8 sectors from superblock
     Update Time : Sun Nov  5 05:09:23 2023
   Bad Block Log : 512 entries available at offset 56 sectors
        Checksum : 6d155c7b - correct
          Events : 5014067

          Layout : left-symmetric
      Chunk Size : 512K

    Device Role : Active device 6
    Array State : .AAAAAA ('A' == active, '.' == missing, 'R' == replacing)

(*2)
# iostat
15:35:10 Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
15:35:10 md127             0.40         0.00         1.60         0.00          0         16          0
15:35:20 md127            80.90        23.20       300.40         0.00        232       3004          0
15:35:30 md127             2.60         0.00        13.60         0.00          0        136          0
15:35:40 md127             1.20         0.00         5.20         0.00          0         52          0
15:35:50 md127            46.00         3.60      1455.60         0.00         36      14556          0
15:36:00 md127             7.50         0.00        43.20         0.00          0        432          0
15:36:10 md127             1.40         0.00        16.00         0.00          0        160          0
15:36:20 md127             2.70         0.00        16.00         0.00          0        160          0
15:36:30 md127             3.20         0.40        37.20         0.00          4        372          0
15:36:40 md127             1.30         0.00        11.60         0.00          0        116          0
15:36:50 md127             3.10         0.40        36.40         0.00          4        364          0
15:37:00 md127             3.00         0.00        98.80         0.00          0        988          0
15:37:10 md127             2.50         0.00        10.80         0.00          0        108          0
15:37:20 md127             1.30         0.00         8.40         0.00          0         84          0
15:37:30 md127             2.60         0.00        16.00         0.00          0        160          0
15:37:40 md127             9.30         0.40        62.80         0.00          4        628          0
15:37:50 md127             8.40         0.00        33.60         0.00          0        336          0
15:38:00 md127             8.80         0.00        42.80         0.00          0        428          0
15:38:00 2023-11-05
15:38:00 Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
15:38:00 md127             5.65        76.85       953.30         0.00   30896031  383252160          0
15:38:10 md127             5.30         0.00        24.40         0.00          0        244          0
15:38:20 md127             1.30         0.00        12.40         0.00          0        124          0
15:38:30 md127             2.60         0.00        11.20         0.00          0        112          0
15:38:40 md127             2.60         0.00        16.40         0.00          0        164          0
15:38:50 md127             3.30         0.40        34.80         0.00          4        348          0
15:39:00 md127             1.30         0.00        11.60         0.00          0        116          0
15:39:10 md127             2.50         0.00        10.00         0.00          0        100          0
15:39:20 md127             2.30         0.00        17.60         0.00          0        176          0
15:39:30 md127             2.70         0.00        20.40         0.00          0        204          0
15:39:40 md127             4.90         1.20       132.80         0.00         12       1328          0
15:39:50 md127             2.70         0.00        11.20         0.00          0        112          0
15:40:00 md127             1.30         0.00        12.80         0.00          0        128          0
15:40:10 md127             2.60         0.00        16.00         0.00          0        160          0
15:40:20 md127             4.30         0.00        64.80         0.00          0        648          0
15:40:30 md127             3.50         0.00        28.80         0.00          0        288          0
15:40:40 md127             2.80         0.00        13.20         0.00          0        132          0
15:40:50 md127             5.00         0.00        23.60         0.00          0        236          0
15:41:00 md127             3.60         0.00        17.20         0.00          0        172          0
15:41:10 md127             2.20         1.60        87.20         0.00         16        872          0
15:41:20 md127             6.00         1.60       361.20         0.00         16       3612          0

(*3)
# iostat -x
          Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
15:35:02 md127            0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00
15:35:02 sdb              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00
15:35:02 sdc              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00
15:35:02 sdd              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00
15:35:02 sde              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00
15:35:02 sdf              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00
15:35:02 sdg              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00
15:35:12 md127            5.80     23.20     0.00   0.00    1.60     4.00    0.40      1.60     0.00   0.00   13.25     4.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.01   1.83
15:35:12 sdb              1.60      6.40     0.00   0.00    0.12     4.00    0.70      2.10     0.10  12.50    5.14     3.00    0.00      0.00     0.00   0.00    0.00     0.00    0.50    6.80    0.01   0.58
15:35:12 sdc              1.70      6.80     0.00   0.00    1.76     4.00    0.70      2.10     0.10  12.50    3.71     3.00    0.00      0.00     0.00   0.00    0.00     0.00    0.50    4.80    0.01   0.76
15:35:12 sdd              1.70      6.80     0.00   0.00    1.18     4.00    0.60      1.30     0.00   0.00   12.33     2.17    0.00      0.00     0.00   0.00    0.00     0.00    0.50    0.40    0.01   1.16
15:35:12 sde              0.20      0.80     0.00   0.00   10.50     4.00    0.50      0.90     0.00   0.00   14.60     1.80    0.00      0.00     0.00   0.00    0.00     0.00    0.50    0.40    0.01   0.96
15:35:12 sdf              0.00      0.00     0.00   0.00    0.00     0.00    0.60      1.30     0.00   0.00   15.67     2.17    0.00      0.00     0.00   0.00    0.00     0.00    0.50    4.40    0.01   0.97
15:35:12 sdg              0.80      3.60     0.10  11.11    4.50     4.50    0.80      2.50     0.10  11.11   13.12     3.12    0.00      0.00     0.00   0.00    0.00     0.00    0.50    3.80    0.02   1.51
15:35:22 md127            0.00      0.00     0.00   0.00    0.00     0.00   75.10    300.40     0.00   0.00   15.81     4.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    1.19   6.22
15:35:22 sdb              0.00      0.00     0.00   0.00    0.00     0.00    1.20    104.15    25.20  95.45    4.00    86.79    0.00      0.00     0.00   0.00    0.00     0.00    0.70    5.57    0.01   0.52
15:35:22 sdc              0.00      0.00     0.00   0.00    0.00     0.00    1.10    103.75    25.20  95.82    5.73    94.32    0.00      0.00     0.00   0.00    0.00     0.00    0.70    7.71    0.01   0.65
15:35:22 sdd              0.00      0.00     0.00   0.00    0.00     0.00    1.00     53.75    12.80  92.75   13.80    53.75    0.00      0.00     0.00   0.00    0.00     0.00    0.70    4.29    0.02   1.45
15:35:22 sde              0.00      0.00     0.00   0.00    0.00     0.00    1.00     52.95    12.60  92.65    9.80    52.95    0.00      0.00     0.00   0.00    0.00     0.00    0.70    2.43    0.01   1.07
15:35:22 sdf              0.00      0.00     0.00   0.00    0.00     0.00    1.00     52.95    12.60  92.65   13.20    52.95    0.00      0.00     0.00   0.00    0.00     0.00    0.70    3.00    0.02   1.37
15:35:22 sdg              0.10     23.60     5.80  98.31   15.00   236.00    1.10     45.35    10.60  90.60   13.73    41.23    0.00      0.00     0.00   0.00    0.00     0.00    0.70    3.29    0.02   1.75
15:35:32 md127            0.00      0.00     0.00   0.00    0.00     0.00    2.60     13.60     0.00   0.00 1410.23     5.23    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    3.67   8.41
15:35:32 sdb              0.00      0.00     0.00   0.00    0.00     0.00    1.40      6.60     0.80  36.36    4.43     4.71    0.00      0.00     0.00   0.00    0.00     0.00    1.00    5.70    0.01   0.73
15:35:32 sdc              0.00      0.00     0.00   0.00    0.00     0.00    1.00      1.80     0.00   0.00    2.80     1.80    0.00      0.00     0.00   0.00    0.00     0.00    1.00    2.60    0.01   0.38
15:35:32 sdd              0.00      0.00     0.00   0.00    0.00     0.00    1.20      9.80     1.80  60.00   12.75     8.17    0.00      0.00     0.00   0.00    0.00     0.00    1.00    2.90    0.02   1.63
15:35:32 sde              0.00      0.00     0.00   0.00    0.00     0.00    1.00      1.80     0.00   0.00   14.20     1.80    0.00      0.00     0.00   0.00    0.00     0.00    1.00    0.30    0.01   1.49
15:35:32 sdf              0.00      0.00     0.00   0.00    0.00     0.00    1.10      2.60     0.10   8.33   12.55     2.36    0.00      0.00     0.00   0.00    0.00     0.00    1.00    1.60    0.02   1.48
15:35:32 sdg              0.00      0.00     0.00   0.00    0.00     0.00    1.70     15.40     2.70  61.36   13.53     9.06    0.00      0.00     0.00   0.00    0.00     0.00    1.00    6.90    0.03   2.36
15:35:42 md127            0.10      0.40     0.00   0.00   20.00     4.00    2.70     41.20     0.00   0.00 1039.07    15.26    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    2.81   8.88
15:35:42 sdb              0.40     28.80     6.80  94.44   14.25    72.00    1.50     32.55     7.10  82.56    4.47    21.70    0.00      0.00     0.00   0.00    0.00     0.00    0.90    6.78    0.02   0.95
15:35:42 sdc              0.40     32.80     7.80  95.12    2.25    82.00    1.10     27.75     6.30  85.14    1.09    25.23    0.00      0.00     0.00   0.00    0.00     0.00    0.90    0.78    0.00   0.28
15:35:42 sdd              0.20      6.80     1.50  88.24    9.00    34.00    1.00      2.15     0.00   0.00   14.80     2.15    0.00      0.00     0.00   0.00    0.00     0.00    0.90    3.78    0.02   1.58
15:35:42 sde              0.20      6.80     1.50  88.24    0.50    34.00    0.90      1.75     0.00   0.00   14.78     1.94    0.00      0.00     0.00   0.00    0.00     0.00    0.90    0.44    0.01   1.43
15:35:42 sdf              0.20     26.00     6.30  96.92   11.50   130.00    1.70     38.15     8.30  83.00    8.35    22.44    0.00      0.00     0.00   0.00    0.00     0.00    0.90    3.00    0.02   1.74
15:35:42 sdg              0.00      0.00     0.00   0.00    0.00     0.00    1.90     16.95     2.80  59.57   12.32     8.92    0.00      0.00     0.00   0.00    0.00     0.00    0.90    7.22    0.03   2.02
15:35:52 md127            0.80      3.20     0.00   0.00   13.75     4.00   43.60   1419.60     0.00   0.00   99.34    32.56    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    4.34  13.86
15:35:52 sdb              0.60     85.20    20.70  97.18   14.33   142.00    2.70    470.15   115.20  97.71    2.07   174.13    0.00      0.00     0.00   0.00    0.00     0.00    0.80    4.25    0.02   1.25
15:35:52 sdc              1.20     97.20    23.10  95.06   10.50    81.00    2.20    371.75    91.10  97.64    2.59   168.98    0.00      0.00     0.00   0.00    0.00     0.00    0.80    2.12    0.02   1.13
15:35:52 sdd              2.10    305.60    74.30  97.25   14.62   145.52    1.70    234.95    57.40  97.12    7.71   138.21    0.00      0.00     0.00   0.00    0.00     0.00    0.80    1.12    0.04   2.43
15:35:52 sde              1.50    288.40    70.60  97.92   17.47   192.27    1.90    278.95    68.20  97.29    9.74   146.82    0.00      0.00     0.00   0.00    0.00     0.00    0.80    0.38    0.05   2.60
15:35:52 sdf              1.30    334.00    82.20  98.44   26.31   256.92    2.30    351.35    85.90  97.39    7.74   152.76    0.00      0.00     0.00   0.00    0.00     0.00    0.80    2.00    0.05   2.34
15:35:52 sdg              0.80    215.20    53.00  98.51   18.38   269.00    2.90    510.55   125.10  97.73    7.03   176.05    0.00      0.00     0.00   0.00    0.00     0.00    0.80    3.75    0.04   2.53
15:36:02 md127            0.00      0.00     0.00   0.00    0.00     0.00    7.50     43.20     0.00   0.00  500.76     5.76    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    3.76   9.00
15:36:02 sdb              0.20     18.40     4.40  95.65   13.00    92.00    1.90     45.40    10.00  84.03    6.37    23.89    0.00      0.00     0.00   0.00    0.00     0.00    1.20    8.25    0.02   1.17
15:36:02 sdc              0.60     32.40     7.50  92.59    9.00    54.00    1.40     21.00     4.40  75.86    3.64    15.00    0.00      0.00     0.00   0.00    0.00     0.00    1.20    3.83    0.01   0.89
15:36:02 sdd              0.40     14.00     3.10  88.57    0.50    35.00    1.20      2.60     0.00   0.00   14.33     2.17    0.00      0.00     0.00   0.00    0.00     0.00    1.20    0.33    0.02   1.89
15:36:02 sde              0.40     14.00     3.10  88.57    2.50    35.00    1.20      2.60     0.00   0.00   14.17     2.17    0.00      0.00     0.00   0.00    0.00     0.00    1.20    0.33    0.02   1.97
15:36:02 sdf              0.60     32.40     7.50  92.59    6.67    54.00    1.50     21.40     4.40  74.58   12.73    14.27    0.00      0.00     0.00   0.00    0.00     0.00    1.20    2.50    0.03   2.19
15:36:02 sdg              0.00      0.00     0.00   0.00    0.00     0.00    1.80     27.40     5.60  75.68   13.44    15.22    0.00      0.00     0.00   0.00    0.00     0.00    1.20    3.67    0.03   2.52
15:36:12 md127            0.00      0.00     0.00   0.00    0.00     0.00    2.80     24.40     0.00   0.00 1312.57     8.71    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    3.68   6.54
15:36:12 sdb              0.10     10.40     2.50  96.15    0.00   104.00    1.60     18.20     3.50  68.63    3.56    11.38    0.00      0.00     0.00   0.00    0.00     0.00    1.10    4.73    0.01   0.67
15:36:12 sdc              0.50     16.00     3.50  87.50    3.40    32.00    1.20     12.60     2.50  67.57    3.00    10.50    0.00      0.00     0.00   0.00    0.00     0.00    1.10    3.00    0.01   0.50
15:36:12 sdd              0.40      5.60     1.00  71.43    0.25    14.00    1.10      2.20     0.00   0.00   14.45     2.00    0.00      0.00     0.00   0.00    0.00     0.00    1.10    0.45    0.02   1.76
15:36:12 sde              0.40      5.60     1.00  71.43    0.25    14.00    1.10      2.20     0.00   0.00   14.73     2.00    0.00      0.00     0.00   0.00    0.00     0.00    1.10    0.36    0.02   1.74
15:36:12 sdf              0.50     16.00     3.50  87.50    3.20    32.00    1.40     21.00     4.40  75.86   13.57    15.00    0.00      0.00     0.00   0.00    0.00     0.00    1.10    2.91    0.02   1.99
15:36:12 sdg              0.00      0.00     0.00   0.00    0.00     0.00    1.70     16.20     2.90  63.04   13.53     9.53    0.00      0.00     0.00   0.00    0.00     0.00    1.10    4.64    0.03   2.41
15:36:22 md127            0.00      0.00     0.00   0.00    0.00     0.00    1.30      7.60     0.00   0.00 1415.46     5.85    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    1.84  12.01
15:36:22 sdb              0.00      0.00     0.00   0.00    0.00     0.00    0.80      3.70     0.40  33.33    2.62     4.62    0.00      0.00     0.00   0.00    0.00     0.00    0.60    3.00    0.00   0.26
15:36:22 sdc              0.20      2.40     0.40  66.67    0.50    12.00    0.60      1.30     0.00   0.00    0.83     2.17    0.00      0.00     0.00   0.00    0.00     0.00    0.60    0.67    0.00   0.13
15:36:22 sdd              0.20      2.40     0.40  66.67    0.50    12.00    0.60      1.30     0.00   0.00   16.17     2.17    0.00      0.00     0.00   0.00    0.00     0.00    0.60    0.33    0.01   1.05
15:36:22 sde              0.20      2.40     0.40  66.67    0.50    12.00    0.60      1.30     0.00   0.00   14.00     2.17    0.00      0.00     0.00   0.00    0.00     0.00    0.60    0.33    0.01   0.91
15:36:22 sdf              0.20      2.40     0.40  66.67    0.50    12.00    0.70      6.50     1.20  63.16   14.71     9.29    0.00      0.00     0.00   0.00    0.00     0.00    0.60    3.17    0.01   1.12
15:36:22 sdg              0.00      0.00     0.00   0.00    0.00     0.00    0.90      8.90     1.60  64.00   14.89     9.89    0.00      0.00     0.00   0.00    0.00     0.00    0.60    4.50    0.02   1.39

(*4)
2023-11-05 15:34:42 Dirty:        60 kB  Buffers:   3990316 kB  MemFree:   1276448 kB
2023-11-05 15:34:52 Dirty:        88 kB  Buffers:   3990332 kB  MemFree:   1292280 kB
2023-11-05 15:35:02 Dirty:       544 kB  Buffers:   3990344 kB  MemFree:   1292780 kB
2023-11-05 15:35:12 Dirty:     94128 kB  Buffers:   3993288 kB  MemFree:   1189540 kB
2023-11-05 15:35:22 Dirty:     96756 kB  Buffers:   3993328 kB  MemFree:   1194372 kB
2023-11-05 15:35:32 Dirty:     96696 kB  Buffers:   3993364 kB  MemFree:   1189540 kB
2023-11-05 15:35:42 Dirty:     96176 kB  Buffers:   3993408 kB  MemFree:   1199604 kB
2023-11-05 15:35:52 Dirty:     81980 kB  Buffers:   3993468 kB  MemFree:   1137836 kB
2023-11-05 15:36:02 Dirty:     82180 kB  Buffers:   3993504 kB  MemFree:   1132644 kB
2023-11-05 15:36:12 Dirty:     81884 kB  Buffers:   3993532 kB  MemFree:   1164068 kB
2023-11-05 15:36:22 Dirty:     81956 kB  Buffers:   3993556 kB  MemFree:   1155296 kB
2023-11-05 15:36:32 Dirty:     81468 kB  Buffers:   3993600 kB  MemFree:   1148428 kB
2023-11-05 15:36:42 Dirty:     81184 kB  Buffers:   3993632 kB  MemFree:   1203772 kB
2023-11-05 15:36:52 Dirty:     80956 kB  Buffers:   3993652 kB  MemFree:   1168112 kB
2023-11-05 15:37:02 Dirty:     80360 kB  Buffers:   3993684 kB  MemFree:   1164228 kB
2023-11-05 15:37:12 Dirty:     80280 kB  Buffers:   3993720 kB  MemFree:   1200968 kB
2023-11-05 15:37:22 Dirty:     80052 kB  Buffers:   3993736 kB  MemFree:   1165204 kB
2023-11-05 15:37:32 Dirty:     79828 kB  Buffers:   3993768 kB  MemFree:   1144772 kB
2023-11-05 15:37:42 Dirty:     79488 kB  Buffers:   3993876 kB  MemFree:   1148376 kB
2023-11-05 15:37:52 Dirty:     79500 kB  Buffers:   3993964 kB  MemFree:   1144604 kB
2023-11-05 15:38:02 Dirty:     79652 kB  Buffers:   3994088 kB  MemFree:   1229132 kB
2023-11-05 15:38:12 Dirty:     79308 kB  Buffers:   3994136 kB  MemFree:   1222776 kB
2023-11-05 15:38:22 Dirty:     79132 kB  Buffers:   3994168 kB  MemFree:   1216236 kB
2023-11-05 15:38:32 Dirty:     79112 kB  Buffers:   3994196 kB  MemFree:   1205308 kB
2023-11-05 15:38:42 Dirty:     78980 kB  Buffers:   3994228 kB  MemFree:   1213188 kB
2023-11-05 15:38:52 Dirty:     79160 kB  Buffers:   3994268 kB  MemFree:   1199640 kB
2023-11-05 15:39:02 Dirty:     79304 kB  Buffers:   3994308 kB  MemFree:   1195604 kB
2023-11-05 15:39:12 Dirty:     78832 kB  Buffers:   3994340 kB  MemFree:   1215976 kB
2023-11-05 15:39:22 Dirty:     78872 kB  Buffers:   3994380 kB  MemFree:   1196416 kB
2023-11-05 15:39:32 Dirty:     78236 kB  Buffers:   3994420 kB  MemFree:   1198744 kB
2023-11-05 15:39:42 Dirty:     77188 kB  Buffers:   3994456 kB  MemFree:   1224896 kB
2023-11-05 15:39:52 Dirty:     77356 kB  Buffers:   3994488 kB  MemFree:   1219820 kB
2023-11-05 15:40:02 Dirty:     77520 kB  Buffers:   3994520 kB  MemFree:   1216344 kB
2023-11-05 15:40:12 Dirty:     77452 kB  Buffers:   3994548 kB  MemFree:   1197372 kB
2023-11-05 15:40:22 Dirty:     76652 kB  Buffers:   3994580 kB  MemFree:   1181344 kB
2023-11-05 15:40:32 Dirty:     76620 kB  Buffers:   3994604 kB  MemFree:   1188504 kB
2023-11-05 15:40:42 Dirty:     76516 kB  Buffers:   3994636 kB  MemFree:   1202256 kB
2023-11-05 15:40:52 Dirty:     76544 kB  Buffers:   3994708 kB  MemFree:   1181708 kB
2023-11-05 15:41:02 Dirty:     76716 kB  Buffers:   3994748 kB  MemFree:   1183688 kB
2023-11-05 15:41:12 Dirty:     74888 kB  Buffers:   3994796 kB  MemFree:   1168440 kB
2023-11-05 15:41:22 Dirty:     72064 kB  Buffers:   3994836 kB  MemFree:   1167124 kB
2023-11-05 15:41:32 Dirty:     71520 kB  Buffers:   3994860 kB  MemFree:   1160128 kB
2023-11-05 15:41:42 Dirty:     71464 kB  Buffers:   3994892 kB  MemFree:   1154912 kB
2023-11-05 15:41:52 Dirty:     71504 kB  Buffers:   3994932 kB  MemFree:   1160312 kB
2023-11-05 15:42:02 Dirty:     71404 kB  Buffers:   3994956 kB  MemFree:   1204212 kB
2023-11-05 15:42:12 Dirty:     70812 kB  Buffers:   3994988 kB  MemFree:   1163440 kB
2023-11-05 15:42:22 Dirty:     69880 kB  Buffers:   3995024 kB  MemFree:   1160820 kB

Then at some point all the dirty blocks are written quickly:

2023-11-05 16:34:13 Dirty:      7876 kB  Buffers:   4042032 kB  MemFree:    628004 kB
2023-11-05 16:34:23 Dirty:      7836 kB  Buffers:   4042056 kB  MemFree:    626240 kB
2023-11-05 16:34:33 Dirty:      7628 kB  Buffers:   4042080 kB  MemFree:    624728 kB
2023-11-05 16:34:43 Dirty:      7540 kB  Buffers:   4042112 kB  MemFree:    622464 kB
2023-11-05 16:34:53 Dirty:      7496 kB  Buffers:   4042136 kB  MemFree:    620448 kB
2023-11-05 16:35:03 Dirty:      8224 kB  Buffers:   4042164 kB  MemFree:    635820 kB
2023-11-05 16:35:13 Dirty:      7544 kB  Buffers:   4042212 kB  MemFree:    631848 kB
2023-11-05 16:35:23 Dirty:      7524 kB  Buffers:   4042236 kB  MemFree:    631092 kB
2023-11-05 16:35:33 Dirty:      7472 kB  Buffers:   4042260 kB  MemFree:    630084 kB
2023-11-05 16:35:43 Dirty:      7320 kB  Buffers:   4042300 kB  MemFree:    625044 kB
2023-11-05 16:35:53 Dirty:      7244 kB  Buffers:   4042324 kB  MemFree:    623788 kB
2023-11-05 16:36:03 Dirty:      7516 kB  Buffers:   4042348 kB  MemFree:    631476 kB
2023-11-05 16:36:13 Dirty:      7216 kB  Buffers:   4042376 kB  MemFree:    636232 kB
2023-11-05 16:36:23 Dirty:      6368 kB  Buffers:   4042408 kB  MemFree:    633964 kB
2023-11-05 16:36:33 Dirty:      5564 kB  Buffers:   4042424 kB  MemFree:    632464 kB
2023-11-05 16:36:43 Dirty:      4452 kB  Buffers:   4042456 kB  MemFree:    630704 kB
2023-11-05 16:36:53 Dirty:      4344 kB  Buffers:   4042480 kB  MemFree:    628688 kB
2023-11-05 16:37:03 Dirty:       296 kB  Buffers:   4042524 kB  MemFree:    625196 kB
2023-11-05 16:37:13 Dirty:       312 kB  Buffers:   4042540 kB  MemFree:    623948 kB
2023-11-05 16:37:23 Dirty:       204 kB  Buffers:   4042548 kB  MemFree:    622216 kB
2023-11-05 16:37:33 Dirty:       240 kB  Buffers:   4042564 kB  MemFree:    620704 kB
2023-11-05 16:37:43 Dirty:        84 kB  Buffers:   4042580 kB  MemFree:    619192 kB
2023-11-05 16:37:53 Dirty:        84 kB  Buffers:   4042588 kB  MemFree:    617428 kB

I have a script that displays progress in this log:

                         Dirty               Buffers               MemFree
2023-11-05 15:34:42        60 kB    -7560   3990316 kB       24   1276448 kB   -43800
2023-11-05 15:34:52        88 kB       28   3990332 kB       16   1292280 kB    15832
2023-11-05 15:35:02       544 kB      456   3990344 kB       12   1292780 kB      500
2023-11-05 15:35:12     94128 kB    93584   3993288 kB     2944   1189540 kB  -103240
2023-11-05 15:35:22     96756 kB     2628   3993328 kB       40   1194372 kB     4832
2023-11-05 15:35:32     96696 kB      -60   3993364 kB       36   1189540 kB    -4832
2023-11-05 15:35:42     96176 kB     -520   3993408 kB       44   1199604 kB    10064
2023-11-05 15:35:52     81980 kB   -14196   3993468 kB       60   1137836 kB   -61768
2023-11-05 15:36:02     82180 kB      200   3993504 kB       36   1132644 kB    -5192
2023-11-05 15:36:12     81884 kB     -296   3993532 kB       28   1164068 kB    31424
2023-11-05 15:36:22     81956 kB       72   3993556 kB       24   1155296 kB    -8772
2023-11-05 15:36:32     81468 kB     -488   3993600 kB       44   1148428 kB    -6868
2023-11-05 15:36:42     81184 kB     -284   3993632 kB       32   1203772 kB    55344
2023-11-05 15:36:52     80956 kB     -228   3993652 kB       20   1168112 kB   -35660
2023-11-05 15:37:02     80360 kB     -596   3993684 kB       32   1164228 kB    -3884
2023-11-05 15:37:12     80280 kB      -80   3993720 kB       36   1200968 kB    36740
2023-11-05 15:37:22     80052 kB     -228   3993736 kB       16   1165204 kB   -35764
2023-11-05 15:37:32     79828 kB     -224   3993768 kB       32   1144772 kB   -20432
2023-11-05 15:37:42     79488 kB     -340   3993876 kB      108   1148376 kB     3604
2023-11-05 15:37:52     79500 kB       12   3993964 kB       88   1144604 kB    -3772
2023-11-05 15:38:02     79652 kB      152   3994088 kB      124   1229132 kB    84528
2023-11-05 15:38:12     79308 kB     -344   3994136 kB       48   1222776 kB    -6356
2023-11-05 15:38:22     79132 kB     -176   3994168 kB       32   1216236 kB    -6540
2023-11-05 15:38:32     79112 kB      -20   3994196 kB       28   1205308 kB   -10928
2023-11-05 15:38:42     78980 kB     -132   3994228 kB       32   1213188 kB     7880
2023-11-05 15:38:52     79160 kB      180   3994268 kB       40   1199640 kB   -13548
2023-11-05 15:39:02     79304 kB      144   3994308 kB       40   1195604 kB    -4036
2023-11-05 15:39:12     78832 kB     -472   3994340 kB       32   1215976 kB    20372
2023-11-05 15:39:22     78872 kB       40   3994380 kB       40   1196416 kB   -19560
2023-11-05 15:39:32     78236 kB     -636   3994420 kB       40   1198744 kB     2328
2023-11-05 15:39:42     77188 kB    -1048   3994456 kB       36   1224896 kB    26152
2023-11-05 15:39:52     77356 kB      168   3994488 kB       32   1219820 kB    -5076
2023-11-05 15:40:02     77520 kB      164   3994520 kB       32   1216344 kB    -3476
2023-11-05 15:40:12     77452 kB      -68   3994548 kB       28   1197372 kB   -18972
2023-11-05 15:40:22     76652 kB     -800   3994580 kB       32   1181344 kB   -16028
2023-11-05 15:40:32     76620 kB      -32   3994604 kB       24   1188504 kB     7160
2023-11-05 15:40:42     76516 kB     -104   3994636 kB       32   1202256 kB    13752
2023-11-05 15:40:52     76544 kB       28   3994708 kB       72   1181708 kB   -20548
2023-11-05 15:41:02     76716 kB      172   3994748 kB       40   1183688 kB     1980
2023-11-05 15:41:12     74888 kB    -1828   3994796 kB       48   1168440 kB   -15248
2023-11-05 15:41:22     72064 kB    -2824   3994836 kB       40   1167124 kB    -1316
2023-11-05 15:41:32     71520 kB     -544   3994860 kB       24   1160128 kB    -6996
2023-11-05 15:41:42     71464 kB      -56   3994892 kB       32   1154912 kB    -5216
2023-11-05 15:41:52     71504 kB       40   3994932 kB       40   1160312 kB     5400
2023-11-05 15:42:02     71404 kB     -100   3994956 kB       24   1204212 kB    43900
2023-11-05 15:42:12     70812 kB     -592   3994988 kB       32   1163440 kB   -40772
2023-11-05 15:42:22     69880 kB     -932   3995024 kB       36   1160820 kB    -2620

(*5)

$ sudo perf top --pid 4164147 -g
Samples: 261K of event 'cycles:P', 4000 Hz, Event count (approx.): 70413169119 lost: 0/0 drop: 0/0
   Children      Self  Shared O  Symbol
+  100.00%     1.60%  [kernel]  [k] ext4_mb_regular_allocator
+   67.08%     5.93%  [kernel]  [k] ext4_mb_find_good_group_avg_frag_lists
+   62.47%    42.34%  [kernel]  [k] ext4_mb_good_group
+   22.51%    11.36%  [kernel]  [k] ext4_get_group_info
+   19.70%    10.80%  [kernel]  [k] ext4_mb_scan_aligned
+   13.13%     0.00%  [kernel]  [k] ret_from_fork_asm
+   13.13%     0.00%  [kernel]  [k] ret_from_fork
+   13.13%     0.00%  [kernel]  [k] kthread
+   13.13%     0.00%  [kernel]  [k] worker_thread
+   13.13%     0.00%  [kernel]  [k] process_one_work
+   13.13%     0.00%  [kernel]  [k] wb_workfn
+   13.13%     0.00%  [kernel]  [k] wb_writeback
+   13.13%     0.00%  [kernel]  [k] __writeback_inodes_wb
+   13.13%     0.00%  [kernel]  [k] writeback_sb_inodes
+   13.13%     0.00%  [kernel]  [k] __writeback_single_inode
+   13.13%     0.00%  [kernel]  [k] do_writepages
+   13.13%     0.00%  [kernel]  [k] ext4_writepages
+   13.13%     0.00%  [kernel]  [k] ext4_do_writepages
+   13.13%     0.00%  [kernel]  [k] ext4_map_blocks
+   13.13%     0.00%  [kernel]  [k] ext4_ext_map_blocks
+   13.13%     0.00%  [kernel]  [k] ext4_mb_new_blocks
+    8.95%     1.80%  [kernel]  [k] mb_find_extent
+    7.11%     1.41%  [kernel]  [k] ext4_mb_load_buddy_gfp
+    6.94%     6.89%  [kernel]  [k] mb_find_order_for_block
+    5.89%     5.79%  [kernel]  [k] __rcu_read_unlock
+    5.43%     0.19%  [kernel]  [k] pagecache_get_page
+    5.14%     0.47%  [kernel]  [k] __filemap_get_folio
+    4.53%     1.61%  [kernel]  [k] filemap_get_entry
+    3.81%     3.75%  [kernel]  [k] __rcu_read_lock
+    2.75%     0.95%  [kernel]  [k] xas_load
+    1.73%     1.53%  [kernel]  [k] xas_descend
+    1.08%     1.08%  [kernel]  [k] ext4_mb_unload_buddy
+    0.76%     0.53%  [kernel]  [k] _raw_read_unlock
+    0.55%     0.55%  [kernel]  [k] _raw_spin_trylock
      0.44%     0.43%  [kernel]  [k] _raw_read_lock
      0.26%     0.24%  [kernel]  [k] xas_start
      0.22%     0.18%  [kernel]  [k] mb_find_buddy
      0.19%     0.14%  [kernel]  [k] folio_mark_accessed
      0.15%     0.15%  [kernel]  [k] _raw_spin_unlock
      0.13%     0.09%  [kernel]  [k] __cond_resched
      0.09%     0.09%  [kernel]  [k] folio_test_hugetlb
      0.09%     0.00%  [kernel]  [k] hrtimer_interrupt
      0.07%     0.00%  [kernel]  [k] __hrtimer_run_queues
      0.04%     0.00%  [kernel]  [k] scheduler_tick
      0.03%     0.00%  [kernel]  [k] __sysvec_apic_timer_interrupt
      0.01%     0.00%  [kernel]  [k] perf_adjust_freq_unthr_context
      0.01%     0.00%  [kernel]  [k] clockevents_program_event
      0.01%     0.00%  [kernel]  [k] arch_scale_freq_tick
      0.01%     0.00%  [kernel]  [k] asm_sysvec_apic_timer_interrupt
      0.01%     0.00%  [kernel]  [k] sysvec_apic_timer_interrupt
      0.01%     0.01%  [kernel]  [k] native_write_msr
      0.01%     0.00%  [kernel]  [k] sched_clock_cpu
      0.01%     0.00%  [kernel]  [k] lapic_next_deadline
      0.01%     0.01%  [kernel]  [k] native_irq_return_iret
      0.01%     0.01%  [kernel]  [k] read_tsc
      0.01%     0.00%  [kernel]  [k] timekeeping_advance
      0.01%     0.01%  [kernel]  [k] native_read_msr
      0.01%     0.00%  [kernel]  [k] ktime_get
      0.01%     0.00%  [kernel]  [k] tick_sched_timer
      0.01%     0.01%  [kernel]  [k] native_sched_clock
      0.01%     0.01%  [kernel]  [k] trigger_load_balance
      0.01%     0.00%  [kernel]  [k] update_rq_clock
      0.00%     0.00%  [kernel]  [k] tick_sched_handle
      0.00%     0.00%  [kernel]  [k] update_process_times
      0.00%     0.00%  [kernel]  [k] irqtime_account_irq
      0.00%     0.00%  [kernel]  [k] __irq_exit_rcu
      0.00%     0.00%  [kernel]  [k] update_curr
      0.00%     0.00%  [kernel]  [k] update_load_avg
      0.00%     0.00%  [kernel]  [k] native_apic_msr_eoi_write
      0.00%     0.00%  [kernel]  [k] wq_worker_tick
      0.00%     0.00%  [kernel]  [k] psi_account_irqtime
      0.00%     0.00%  [kernel]  [k] error_entry
      0.00%     0.00%  [kernel]  [k] _raw_spin_lock_irqsave
      0.00%     0.00%  [kernel]  [k] _raw_spin_lock
      0.00%     0.00%  [kernel]  [k] hrtimer_active
      0.00%     0.00%  [kernel]  [k] __update_load_avg_cfs_rq
      0.00%     0.00%  [kernel]  [k] generic_exec_single
      0.00%     0.00%  [kernel]  [k] perf_pmu_nop_void
      0.00%     0.00%  [kernel]  [k] perf_event_task_tick
      0.00%     0.00%  [kernel]  [k] __intel_pmu_enable_all.isra.0
      0.00%     0.00%  [kernel]  [k] task_tick_fair
      0.00%     0.00%  [kernel]  [k] timerqueue_del
      0.00%     0.00%  [kernel]  [k] timekeeping_update
      0.00%     0.00%  [kernel]  [k] rb_erase
      0.00%     0.00%  [kernel]  [k] cpuacct_charge
      0.00%     0.00%  [kernel]  [k] profile_tick
      0.00%     0.00%  [kernel]  [k] hrtimer_forward
      0.00%     0.00%  [kernel]  [k] irqtime_account_process_tick
      0.00%     0.00%  [kernel]  [k] update_irq_load_avg
      0.00%     0.00%  [kernel]  [k] raid5_get_active_stripe
      0.00%     0.00%  [kernel]  [k] rcu_sched_clock_irq
      0.00%     0.00%  [kernel]  [k] kthread_data
      0.00%     0.00%  [kernel]  [k] rcu_segcblist_ready_cbs
      0.00%     0.00%  [kernel]  [k] irqentry_enter
      0.00%     0.00%  [kernel]  [k] hrtimer_run_queues
      0.00%     0.00%  [kernel]  [k] perf_event_nmi_handler
      0.00%     0.00%  [kernel]  [k] enqueue_hrtimer
      0.00%     0.00%  [kernel]  [k] _raw_spin_unlock_irqrestore
      0.00%     0.00%  [kernel]  [k] wbc_detach_inode
      0.00%     0.00%  [kernel]  [k] update_vsyscall
      0.00%     0.00%  [kernel]  [k] timerqueue_add
      0.00%     0.00%  [kernel]  [k] _raw_spin_lock_irq
      0.00%     0.00%  [kernel]  [k] llist_add_batch
      0.00%     0.00%  [kernel]  [k] tick_do_update_jiffies64
      0.00%     0.00%  [kernel]  [k] call_function_single_prep_ipi
      0.00%     0.00%  [kernel]  [k] update_cfs_group
      0.00%     0.00%  [kernel]  [k] __hrtimer_next_event_base
      0.00%     0.00%  [kernel]  [k] notifier_call_chain
      0.00%     0.00%  [kernel]  [k] bio_alloc_bioset
      0.00%     0.00%  [kernel]  [k] __update_load_avg_se
      0.00%     0.00%  [kernel]  [k] account_process_tick
      0.00%     0.00%  [kernel]  [k] pvclock_gtod_notify
      0.00%     0.00%  [kernel]  [k] kmem_cache_free
      0.00%     0.00%  [kernel]  [k] ktime_get_update_offsets_now
      0.00%     0.00%  [kernel]  [k] load_balance
      0.00%     0.00%  [kernel]  [k] update_fast_timekeeper
      0.00%     0.00%  [kernel]  [k] restore_regs_and_return_to_kernel
      0.00%     0.00%  [kernel]  [k] find_get_stripe
      0.00%     0.00%  [kernel]  [k] set_next_buddy
      0.00%     0.00%  [kernel]  [k] ext4_sb_block_valid
      0.00%     0.00%  [kernel]  [k] update_min_vruntime
      0.00%     0.00%  [kernel]  [k] irq_work_tick
      0.00%     0.00%  [kernel]  [k] md_account_bio
      0.00%     0.00%  [kernel]  [k] run_posix_cpu_timers
      0.00%     0.00%  [kernel]  [k] __accumulate_pelt_segments
      0.00%     0.00%  [kernel]  [k] __es_remove_extent
      0.00%     0.00%  [kernel]  [k] ntp_tick_length
      0.00%     0.00%  [kernel]  [k] tick_program_event
      0.00%     0.00%  [kernel]  [k] kmem_cache_alloc
      0.00%     0.00%  [kernel]  [k] __sysvec_call_function_single


(*6)

# echo w > /proc/sysrq-trigger
Nov  5 15:39:42 e7 kernel: sysrq: Show Blocked State
Nov  5 15:39:42 e7 kernel: task:md127_raid6     state:D stack:0     pid:909   ppid:2      flags:0x00004000
Nov  5 15:39:42 e7 kernel: Call Trace:
Nov  5 15:39:42 e7 kernel: <TASK>
Nov  5 15:39:42 e7 kernel: ? __pfx_md_thread+0x10/0x10
Nov  5 15:39:42 e7 kernel: __schedule+0x3ee/0x14c0
Nov  5 15:39:42 e7 kernel: ? update_load_avg+0x7e/0x780
Nov  5 15:39:42 e7 kernel: ? __pfx_md_thread+0x10/0x10
Nov  5 15:39:42 e7 kernel: schedule+0x5e/0xd0
Nov  5 15:39:42 e7 kernel: percpu_ref_switch_to_atomic_sync+0x9a/0xf0
Nov  5 15:39:42 e7 kernel: ? __pfx_autoremove_wake_function+0x10/0x10
Nov  5 15:39:42 e7 kernel: set_in_sync+0x5c/0xc0
Nov  5 15:39:42 e7 kernel: md_check_recovery+0x356/0x5a0
Nov  5 15:39:42 e7 kernel: raid5d+0x76/0x750 [raid456]
Nov  5 15:39:42 e7 kernel: ? lock_timer_base+0x61/0x80
Nov  5 15:39:42 e7 kernel: ? prepare_to_wait_event+0x60/0x180
Nov  5 15:39:42 e7 kernel: ? __pfx_md_thread+0x10/0x10
Nov  5 15:39:42 e7 kernel: md_thread+0xab/0x190
Nov  5 15:39:42 e7 kernel: ? __pfx_autoremove_wake_function+0x10/0x10
Nov  5 15:39:42 e7 kernel: kthread+0xe5/0x120
Nov  5 15:39:42 e7 kernel: ? __pfx_kthread+0x10/0x10
Nov  5 15:39:42 e7 kernel: ret_from_fork+0x31/0x50
Nov  5 15:39:42 e7 kernel: ? __pfx_kthread+0x10/0x10
Nov  5 15:39:42 e7 kernel: ret_from_fork_asm+0x1b/0x30
Nov  5 15:39:42 e7 kernel: </TASK>

# echo l > /proc/sysrq-trigger
Nov  5 15:42:41 e7 kernel: Sending NMI from CPU 3 to CPUs 0-2,4-7:
Nov  5 15:42:41 e7 kernel: NMI backtrace for cpu 1
Nov  5 15:42:41 e7 kernel: CPU: 1 PID: 4164147 Comm: kworker/u16:3 Not tainted 6.5.8-200.fc38.x86_64 #1
Nov  5 15:42:41 e7 kernel: Hardware name: Gigabyte Technology Co., Ltd. Z390 UD/Z390 UD, BIOS F8 05/24/2019
Nov  5 15:42:41 e7 kernel: Workqueue: writeback wb_workfn (flush-9:127)
Nov  5 15:42:41 e7 kernel: RIP: 0010:ext4_mb_good_group+0x60/0xf0
Nov  5 15:42:41 e7 kernel: Code: 48 8b 00 a8 04 75 2c 8b 46 14 85 c0 74 25 8b 4e 18 85 c9 74 1e 83 fb 03 74 3c 83 fb 04 74 23 83 eb 01 83 fb 01 77 38 99 f7 f9 <41> 3b 45 2c 0f 9d c2 eb 02 31 d2 5b 89 d0 5d 41 5c 41 5d c3 cc cc
Nov  5 15:42:41 e7 kernel: RSP: 0018:ffffb7be054ef6a0 EFLAGS: 00000246
Nov  5 15:42:41 e7 kernel: RAX: 0000000000000201 RBX: 0000000000000001 RCX: 000000000000000d
Nov  5 15:42:41 e7 kernel: RDX: 0000000000000003 RSI: ffff892f46d37450 RDI: ffff893019445280
Nov  5 15:42:41 e7 kernel: RBP: 0000000000001306 R08: ffff892f49711000 R09: 0000000000000280
Nov  5 15:42:41 e7 kernel: R10: 0000000000000001 R11: 0000000000000100 R12: 0000000000000004
Nov  5 15:42:41 e7 kernel: R13: ffff892f486d31c8 R14: 0000000000000002 R15: ffff892f46d37450
Nov  5 15:42:41 e7 kernel: FS:  0000000000000000(0000) GS:ffff8936de440000(0000) knlGS:0000000000000000
Nov  5 15:42:41 e7 kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Nov  5 15:42:41 e7 kernel: CR2: 000055d6aaa70af8 CR3: 000000050f222003 CR4: 00000000003706e0
Nov  5 15:42:41 e7 kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
Nov  5 15:42:41 e7 kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Nov  5 15:42:41 e7 kernel: Call Trace:
Nov  5 15:42:41 e7 kernel: <NMI>
Nov  5 15:42:41 e7 kernel: ? nmi_cpu_backtrace+0x99/0x110
Nov  5 15:42:41 e7 kernel: ? nmi_cpu_backtrace_handler+0x11/0x20
Nov  5 15:42:41 e7 kernel: ? nmi_handle+0x5e/0x150
Nov  5 15:42:41 e7 kernel: ? default_do_nmi+0x40/0x100
Nov  5 15:42:41 e7 kernel: ? exc_nmi+0x139/0x1c0
Nov  5 15:42:41 e7 kernel: ? end_repeat_nmi+0x16/0x67
Nov  5 15:42:41 e7 kernel: ? ext4_mb_good_group+0x60/0xf0
Nov  5 15:42:41 e7 kernel: ? ext4_mb_good_group+0x60/0xf0
Nov  5 15:42:41 e7 kernel: ? ext4_mb_good_group+0x60/0xf0
Nov  5 15:42:41 e7 kernel: </NMI>
Nov  5 15:42:41 e7 kernel: <TASK>
Nov  5 15:42:41 e7 kernel: ext4_mb_find_good_group_avg_frag_lists+0x8e/0xe0
Nov  5 15:42:41 e7 kernel: ext4_mb_regular_allocator+0x473/0xe00
Nov  5 15:42:41 e7 kernel: ext4_mb_new_blocks+0xa74/0x11e0
Nov  5 15:42:41 e7 kernel: ? ext4_find_extent+0x3c6/0x420
Nov  5 15:42:41 e7 kernel: ext4_ext_map_blocks+0x5f8/0x1930
Nov  5 15:42:41 e7 kernel: ? release_pages+0x177/0x510
Nov  5 15:42:41 e7 kernel: ? filemap_get_folios_tag+0x1d0/0x200
Nov  5 15:42:41 e7 kernel: ? __folio_batch_release+0x1f/0x60
Nov  5 15:42:41 e7 kernel: ? mpage_prepare_extent_to_map+0x494/0x4d0
Nov  5 15:42:41 e7 kernel: ext4_map_blocks+0x1ba/0x5f0
Nov  5 15:42:41 e7 kernel: ext4_do_writepages+0x76a/0xc90
Nov  5 15:42:41 e7 kernel: ext4_writepages+0xad/0x180
Nov  5 15:42:41 e7 kernel: do_writepages+0xcf/0x1e0
Nov  5 15:42:41 e7 kernel: __writeback_single_inode+0x3d/0x360
Nov  5 15:42:41 e7 kernel: ? wbc_detach_inode+0x101/0x220
Nov  5 15:42:41 e7 kernel: writeback_sb_inodes+0x1ed/0x4b0
Nov  5 15:42:41 e7 kernel: __writeback_inodes_wb+0x4c/0xf0
Nov  5 15:42:41 e7 kernel: wb_writeback+0x298/0x310
Nov  5 15:42:41 e7 kernel: wb_workfn+0x35b/0x510
Nov  5 15:42:41 e7 kernel: ? __schedule+0x3f6/0x14c0
Nov  5 15:42:41 e7 kernel: process_one_work+0x1de/0x3f0
Nov  5 15:42:41 e7 kernel: worker_thread+0x51/0x390
Nov  5 15:42:41 e7 kernel: ? __pfx_worker_thread+0x10/0x10
Nov  5 15:42:41 e7 kernel: kthread+0xe5/0x120
Nov  5 15:42:41 e7 kernel: ? __pfx_kthread+0x10/0x10
Nov  5 15:42:41 e7 kernel: ret_from_fork+0x31/0x50
Nov  5 15:42:41 e7 kernel: ? __pfx_kthread+0x10/0x10
Nov  5 15:42:41 e7 kernel: ret_from_fork_asm+0x1b/0x30
Nov  5 15:42:41 e7 kernel: </TASK>

# echo l > /proc/sysrq-trigger
Nov  5 15:45:47 e7 kernel: sysrq: Show backtrace of all active CPUs
Nov  5 15:45:47 e7 kernel: Sending NMI from CPU 3 to CPUs 0-2,4-7:
Nov  5 15:45:47 e7 kernel: NMI backtrace for cpu 1
Nov  5 15:45:47 e7 kernel: CPU: 1 PID: 4164147 Comm: kworker/u16:3 Not tainted 6.5.8-200.fc38.x86_64 #1
Nov  5 15:45:47 e7 kernel: Hardware name: Gigabyte Technology Co., Ltd. Z390 UD/Z390 UD, BIOS F8 05/24/2019
Nov  5 15:45:47 e7 kernel: Workqueue: writeback wb_workfn (flush-9:127)
Nov  5 15:45:47 e7 kernel: RIP: 0010:ext4_get_group_info+0x47/0x70
Nov  5 15:45:47 e7 kernel: Code: fd 53 8b 88 b0 00 00 00 89 f3 48 8b 40 38 41 d3 ec 48 83 e8 01 21 c3 e8 47 3c c9 ff 48 8b 85 80 03 00 00 48 8b 80 b8 02 00 00 <4a> 8b 2c e0 e8 b0 6a c9 ff 48 8b 44 dd 00 5b 5d 41 5c c3 cc cc cc
Nov  5 15:45:47 e7 kernel: RSP: 0018:ffffb7be054ef680 EFLAGS: 00000202
Nov  5 15:45:47 e7 kernel: RAX: ffff892f5cc30000 RBX: 0000000000000029 RCX: 0000000000000006
Nov  5 15:45:47 e7 kernel: RDX: ffff893019445280 RSI: 00000000000012e9 RDI: ffff892f49711000
Nov  5 15:45:47 e7 kernel: RBP: ffff892f49711000 R08: ffff892f49711000 R09: 0000000000000023
Nov  5 15:45:47 e7 kernel: R10: 0000000000000000 R11: 0000000000000000 R12: 000000000000004b
Nov  5 15:45:47 e7 kernel: R13: ffff892f486d31c8 R14: 0000000000000001 R15: ffff892f46d36730
Nov  5 15:45:47 e7 kernel: FS:  0000000000000000(0000) GS:ffff8936de440000(0000) knlGS:0000000000000000
Nov  5 15:45:47 e7 kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Nov  5 15:45:47 e7 kernel: CR2: 000055d6aaa70af8 CR3: 000000050f222003 CR4: 00000000003706e0
Nov  5 15:45:47 e7 kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
Nov  5 15:45:47 e7 kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Nov  5 15:45:47 e7 kernel: Call Trace:
Nov  5 15:45:47 e7 kernel: <NMI>
Nov  5 15:45:47 e7 kernel: ? nmi_cpu_backtrace+0x99/0x110
Nov  5 15:45:47 e7 kernel: ? nmi_cpu_backtrace_handler+0x11/0x20
Nov  5 15:45:47 e7 kernel: ? nmi_handle+0x5e/0x150
Nov  5 15:45:47 e7 kernel: ? default_do_nmi+0x40/0x100
Nov  5 15:45:47 e7 kernel: ? exc_nmi+0x139/0x1c0
Nov  5 15:45:47 e7 kernel: ? end_repeat_nmi+0x16/0x67
Nov  5 15:45:47 e7 kernel: ? ext4_get_group_info+0x47/0x70
Nov  5 15:45:47 e7 kernel: ? ext4_get_group_info+0x47/0x70
Nov  5 15:45:47 e7 kernel: ? ext4_get_group_info+0x47/0x70
Nov  5 15:45:47 e7 kernel: </NMI>
Nov  5 15:45:47 e7 kernel: <TASK>
Nov  5 15:45:47 e7 kernel: ext4_mb_good_group+0x29/0xf0
Nov  5 15:45:47 e7 kernel: ext4_mb_find_good_group_avg_frag_lists+0x8e/0xe0
Nov  5 15:45:47 e7 kernel: ext4_mb_regular_allocator+0xb74/0xe00
Nov  5 15:45:47 e7 kernel: ext4_mb_new_blocks+0xa74/0x11e0
Nov  5 15:45:47 e7 kernel: ? ext4_find_extent+0x3c6/0x420
Nov  5 15:45:47 e7 kernel: ext4_ext_map_blocks+0x5f8/0x1930
Nov  5 15:45:47 e7 kernel: ? release_pages+0x177/0x510
Nov  5 15:45:47 e7 kernel: ? filemap_get_folios_tag+0x1d0/0x200
Nov  5 15:45:47 e7 kernel: ? __folio_batch_release+0x1f/0x60
Nov  5 15:45:47 e7 kernel: ? mpage_prepare_extent_to_map+0x494/0x4d0
Nov  5 15:45:47 e7 kernel: ext4_map_blocks+0x1ba/0x5f0
Nov  5 15:45:47 e7 kernel: ext4_do_writepages+0x76a/0xc90
Nov  5 15:45:47 e7 kernel: ext4_writepages+0xad/0x180
Nov  5 15:45:47 e7 kernel: do_writepages+0xcf/0x1e0
Nov  5 15:45:47 e7 kernel: __writeback_single_inode+0x3d/0x360
Nov  5 15:45:47 e7 kernel: ? wbc_detach_inode+0x101/0x220
Nov  5 15:45:47 e7 kernel: writeback_sb_inodes+0x1ed/0x4b0
Nov  5 15:45:47 e7 kernel: __writeback_inodes_wb+0x4c/0xf0
Nov  5 15:45:47 e7 kernel: wb_writeback+0x298/0x310
Nov  5 15:45:47 e7 kernel: wb_workfn+0x35b/0x510
Nov  5 15:45:47 e7 kernel: ? __schedule+0x3f6/0x14c0
Nov  5 15:45:47 e7 kernel: process_one_work+0x1de/0x3f0
Nov  5 15:45:47 e7 kernel: worker_thread+0x51/0x390
Nov  5 15:45:47 e7 kernel: ? __pfx_worker_thread+0x10/0x10
Nov  5 15:45:47 e7 kernel: kthread+0xe5/0x120
Nov  5 15:45:47 e7 kernel: ? __pfx_kthread+0x10/0x10
Nov  5 15:45:47 e7 kernel: ret_from_fork+0x31/0x50
Nov  5 15:45:47 e7 kernel: ? __pfx_kthread+0x10/0x10
Nov  5 15:45:47 e7 kernel: ret_from_fork_asm+0x1b/0x30
Nov  5 15:45:47 e7 kernel: </TASK>

(*7)
When the rsync ran the first time I did not see the kthread but decided a restart will clear the issue (I blamed rsyn).
The system could not shutdown and a syseq 'b' was required.
On restart the array was all spares. It was reassembled with
     mdadm --assemble --force /dev/md127 /dev/sd{b,c,d,e,f,g}1
and then a boot looked OK.

Later, examining the logs I saw this message as the array was assembled:
     2023-10-30T01:08:25+1100 kernel: md: requested-resync of RAID array md127
I did not see a resync in mdstat after a restart.

All of the tests in this report were done after these events.


--
Eyal at Home (eyal@xxxxxxxxxxxxxx)




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