[lustre-discuss] Cannot set ost.OSS.ost.thread_started

[Youbiao He]

Thank you very much for your answer. It helps a lot. My Lustre version is
2.10.

For thread_min, when I set it to a number larger than 12, everything works
well, but when I set it to a number smaller than 12, whatever value I set,
it shows 8.

   # lctl set_param ost.OSS.ost.threads_min=10
    ost.OSS.ost.threads_min=10
    # lctl get_param ost.OSS.ost.threads_min
    ost.OSS.ost.threads_max=8

My cluster has 4 OSS and 3 clients.

On Tue, Nov 3, 2020 at 5:00 PM Andreas Dilger <adilger at dilger.ca> wrote:

> On Nov 3, 2020, at 9:25 AM, Youbiao He <yh54 at iastate.edu> wrote:
> > I have installed lustre file system on CentOS. It works well when I
> write or read files. But when I try to set the thread_started and
> thread_min for oss services, I met the following problem.
>
> It is always important to include the Lustre release version that you are
> using in any problem report.
>
> > To set parameters, I run: "sudo lctl set_param
> ost.OSS.ost.threads_started=36"
> > then, I check the setting value by running: "lctl get_param
> ost.OSS.ost.threads_started", and then it shows
> "ost.OSS.ost.threads_started=21". So I can not change the parameter
> "ost.OSS.ost.threads_started".
>
> The "threads_started" parameter is read-only, and lists the number of
> threads currently running. I agree that "lctl set_param" should probably
> print an error for the user in this case.  You can see which parameters are
> writable by the '=' after the parameter name:
>
>     $ lctl list_param -F ost.OSS.ost.threads*
>     ost.OSS.ost.threads_max=
>     ost.OSS.ost.threads_min=
>     ost.OSS.ost.threads_started
>
> The underlying writable /proc or /sys files also has mode 644 instead of
> 444:
>
>     $ ls -l /proc/fs/lustre/ost/OSS/ost/threads_*
>     0 -rw-r--r-- 1 root root 0 Nov  3 15:53
> /proc/fs/lustre/ost/OSS/ost/threads_max
>     0 -rw-r--r-- 1 root root 0 Nov  3 15:53
> /proc/fs/lustre/ost/OSS/ost/threads_min
>     0 -r--r--r-- 1 root root 0 Nov  3 15:53
> /proc/fs/lustre/ost/OSS/ost/threads_started
>
> There *is* an non-zero command status returned to the caller, but it is
> not obvious:
>
>     # lctl set_param ost.OSS.ost.threads_started=38
>     # echo $?
>     5
>
>
> > Another problem is on the parameter "ost.OSS.ost.threads_min", When I
> set it to 10 using lctl, and it shows the parameter is set to 8, not 10.
>
> In my testing, this seems to work OK:
>
>     # lctl get_param ost.OSS.ost.*thread*
>     ost.OSS.ost.threads_max=64
>     ost.OSS.ost.threads_min=3
>     ost.OSS.ost.threads_started=36
>     # lctl set_param ost.OSS.ost.threads_min=8
>     ost.OSS.ost.threads_min=8
>     # lctl get_param ost.OSS.ost.*thread*
>     ost.OSS.ost.threads_max=64
>     ost.OSS.ost.threads_min=8
>     ost.OSS.ost.threads_started=36
>
> Writing to threads_min at runtime doesn't change the current number of
> running threads.  More service threads are only started when there are
> enough concurrently processed requests to start new threads, but it will no
> longer *stop* threads once threads_min is hit.
>
>     # lctl set_param ost.OSS.ost.threads_min=48
>     ost.OSS.ost.threads_min=48
>     # lctl get_param ost.OSS.ost.threads*
>     ost.OSS.ost.threads_max=64
>     ost.OSS.ost.threads_min=48
>     ost.OSS.ost.threads_started=36
>
> Cheers, Andreas
>
>
>
>
>
>
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