zfskern{txg_thread_enter} thread using 100% or more CPU

[Greg V]

On Wed, Apr 25, 2018 at 2:30 AM, Steve Wills <swills at FreeBSD.org> wrote:
> Hi,
> 
> Recently on multiple systems running CURRENT, I've been seeing the 
> system become unresponsive. Leaving top(1) running has lead me to 
> notice that when this happens, the system is still responding to ping 
> and top over ssh is still working, but no new processes can start and 
> switching to other tasks doesn't work. In top, I do see pid 17, 
> [zfskern{txg_thread_enter}] monopolizing both CPU usage and disk IO. 
> Any ideas how to troubleshoot this? It doesn't appear to be a 
> hardware issue.
Hi,

Do you have something writing to a gzip compressed dataset? You can use 
the vfssnoop DTrace script from 
https://forums.freebsd.org/threads/sharing-of-dtrace-scripts.32855/#post-181816 
to see who's writing what.

I don't remember if it was exactly txg_thread_enter or whatever, but 
both CPU and disk sounds a lot like heavily compressed writes.

In my case, the Epiphany browser was downloading a large malware 
database to ~/.config/epiphany/gsb-threats.db :D