Troubleshooting kernel panic with zfs

Mike Tancsa mike at
Fri Sep 21 13:04:41 UTC 2018

On 9/20/2018 8:27 PM, Josh Gitlin wrote:
> My hunch is that, given this was inside kmem_malloc, we were unable to allocate memory for a zio_write_compress call (the pool does have ZFS compression on) and hence this is a tuning issue and not a bug... but I am looking for confirmation and/or suggested changes/troubleshooting steps. The ZFS tuning configuration has been stable for years, to it may be a change in behavior or traffic... If this looks like it might be a bug, I will be able to get more information from a minidump if it reoccurs and can follow up on this thread.

Given all the issues with memory pressure perhaps ARC is eating too
much, I would try artificially limiting it so it does not eat up too
much RAM.  We had a similar purposed server but with 32G RAM and I found
one day the system was randomly shooting processes to reclaim RAM

pid xxx (yyy), uid zzzz, was killed: out of swap space


sysctl -w vfs.zfs.arc_max=6000000000



Mike Tancsa, tel +1 519 651 3400 x203
Sentex Communications, mike at
Providing Internet services since 1994
Cambridge, Ontario Canada

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