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Constant Load of 1.0 on fresh Ubuntu Server installation on Raspberry Pi 4

es flag
DaWastl

My system, which I freshly installed yesterday has a constant load of about 1 and I don't know why.

I have Ubuntu 21.04 64bit server running on RasPi4 cased in a DeskPi Pro V2. There is a 4TB HDD installed which the system is run from.

Installation on the HardDisk I did based on this tutorial https://jamesachambers.com/raspberry-pi-4-ubuntu-20-04-usb-mass-storage-boot-guide/

I can't find any reason why the load is always about 1.0 and the disk never spins down.

ubuntu@maunakea:~$ top -b -n 1 | head -n 16
top - 05:53:55 up 35 min,  1 user,  load average: 0.94, 0.94, 0.92
Tasks: 151 total,   1 running, 150 sleeping,   0 stopped,   0 zombie
%Cpu(s):  1.2 us,  5.0 sy,  0.0 ni, 93.8 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
MiB Mem :   7808.9 total,   6853.6 free,    284.7 used,    670.6 buff/cache
MiB Swap:      0.0 total,      0.0 free,      0.0 used.   7066.6 avail Mem 

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
   4038 ubuntu    20   0   11868   3256   2856 R  17.6   0.0   0:00.06 top
      1 root      20   0  170100  12212   6984 S   0.0   0.2   0:43.28 systemd
      2 root      20   0       0      0      0 S   0.0   0.0   0:00.02 kthreadd
      3 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 rcu_gp
      4 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 rcu_par_gp
      6 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 kworker/0:0H-events_highpri
      8 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 mm_percpu_wq
      9 root      20   0       0      0      0 S   0.0   0.0   0:00.00 rcu_tasks_kthre
     10 root      20   0       0      0      0 S   0.0   0.0   0:00.00 rcu_tasks_rude_
ubuntu@maunakea:~$ sudo iotop -b |head -n 12
Total DISK READ:         0.00 B/s | Total DISK WRITE:         0.00 B/s
Current DISK READ:       0.00 B/s | Current DISK WRITE:       0.00 B/s
    TID  PRIO  USER     DISK READ  DISK WRITE  SWAPIN      IO    COMMAND
      1 ?sys root        0.00 B/s    0.00 B/s  0.00 %  0.00 % init fixrtc splash
      2 ?sys root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [kthreadd]
      3 ?sys root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [rcu_gp]
      4 ?sys root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [rcu_par_gp]
      6 ?sys root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [kworker/0:0H-events_highpri]
      8 ?sys root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [mm_percpu_wq]
      9 ?sys root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [rcu_tasks_kthre]
     10 ?sys root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [rcu_tasks_rude_]
     11 ?sys root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [rcu_tasks_trace]

Remark: The high CPU percentage reported for top is a bit misleading due to batch mode used here for top. In interactive mode it quickly settles down but to ~ 1% but system Load stays high.

What can I else do to track down which process is creating the load?

Also based on htop I can't see why the system should have a load of 1 (sorry I don't know how to get a text output from htop...)

htop output

Thanks for all your comments. In the end Nate gave me the right hint.

It seems only to happen when the system is booted without SD card. Having a Ubuntu SD card inserted the OS also is loaded from HDD and the system load is as expected!

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Soren A avatar
mx flag
Soren A
From the top output, it looks like it is `top` itself that generates the load. It uses 17% in your example. Please try to run top without options and without piping it to head, then you will see live what processes the uses resources over time.
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Artur Meinild avatar
vn flag
Artur Meinild
Also, please try running `htop` and see what it reports.
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es flag
DaWastl
The high CPU % reported for top is just when calling top in batch mode. When calling top in interactive mode it very soon settles down but Load stays high. Result of htop i added above now. Sorry this is the first time I post a question here so I hope I use the platform as intend….
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es flag
DaWastl
On my second RasPi V2 - also on 21.04 - which acts as my router top only generates a load of ~ 0.1 so I would discard top as the source of the load I see on the other machine.
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Nate T avatar
it flag
Nate T
have you run ay other OS's with this hardware combo? Also, you aren't somehow running from swap, are you? The disk is only called on to load programs into memory and to access swap (disk-based virtual memory.)
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es flag
DaWastl
I directly installed Ubuntu yesterday after the box arrived. So it is the first OS running. Swap isn't used at all as you can see in the output of top. Memory is barely used at all in the moment. I can start Raspbian from card to check how behaviour is there....
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Jan Schiefer avatar
ao flag
Jan Schiefer
Nice resolution, fixed the same problem on my 21.04 desktop also. I would be curious what causes this, must be in the kernel? fuser on the sd card device comes up empty.
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