[Bug 270975] [hang] system hangs with heavy io and regular syncing

From: <bugzilla-noreply_at_freebsd.org>
Date: Fri, 21 Apr 2023 14:23:28 UTC

Daniel Ebdrup Jensen <debdrup@freebsd.org> changed:

           What    |Removed                     |Added
                 CC|                            |debdrup@freebsd.org

--- Comment #1 from Daniel Ebdrup Jensen <debdrup@freebsd.org> ---
It sounds to me like console interactivity is being completely overloaded as
there are simply no spare cycles - as such, I'm not sure this is a bug, as
FreeBSD is doing what it's been told to do.

I once manged to do the exact same on a production system, and solved it by
using top -q as root to identify the process and kill it - but it took 3 days
of waiting on the login prompt to finish, and ssh never managed to work.

The kern.sched MIB in sysctl(8) has some control over interactivity and
threshold scores that you can try tweaking to improve this if you can't bear to
shut down the system to fix the issue.

As an alternative, you can use cpuset(8) and/or rctl(8) to limit which cores
your CPUs are running on and/or how much cputime they get, which should free up
cycles for the system to be a little interactive.

If you want help with something, a bug tracker isn't the best place for it -
stop by #FreeBSD on Libera, it's possible that there's someone that can help
you rootcause the issue.
For reference, there's documentation on how to write a good bug report once
you've figured out the exact issue:

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