ZFS "stalls" -- and maybe we should be talking about defaults?

John-Mark Gurney jmg at funkthat.com
Thu Mar 7 06:55:44 UTC 2013

Karl Denninger wrote this message on Tue, Mar 05, 2013 at 06:56 -0600:
> When it happens on my system anything that is CPU-bound continues to
> execute.  I can switch consoles and network I/O also works.  If I have
> an iostat running at the time all I/O counters go to and remain at zero
> while the stall is occurring, but the process that is producing the
> iostat continues to run and emit characters whether it is a ssh session
> or on the physical console.  
> The CPUs are running and processing, but all threads block if they
> attempt access to the disk I/O subsystem, irrespective of the portion of
> the disk I/O subsystem they attempt to access (e.g. UFS, swap or ZFS)  I
> therefore cannot start any new process that requires image activation.

Since it seems like there is a thread that is spinning... Has anyone
thought to modify kgdb to mlockall it's memory and run it against the
current system (kgdb /boot/kernel/kernel /dev/mem), and then when the
thread goes busy, use kgdb to see what where it's spinning?

Just a thought...

  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."

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