Re: arc_prune thread consuming 100% CPU

On 06/10/2023 01:54, Mark Johnston wrote:
> Sometime in the past two months I started seeing a problem with ZFS on 
> the latest FreeBSD main on my desktop. The symptom is that the arc_prune 
> thread, which attempts to shrink the vnode cache, consumes 100% CPU even 
> when the system is idle.

I've been seeing this since around the beginning of September on 
STABLE/13 -- right after I updated because of FreeBSD-SA-23:10.pf etc.

This doesn't affect me while the system is idle, but anything that 
involves some amount of disk IP triggers the effect: that can be as 
simple as running `git status` in a checked out ports repository.  Git 
launches about 20 -- 30 threads, arc_prune immediately pegs one of the 
two CPUs to 100% usage, the system load goes to about 10 and more likely 
than not my PPP link drops.

This is a fairly old Core2 Duo machine with 8GB RAM, which is pretty 
feeble by modern standards, but it's been fine under the sort of loads 
I've put on it until recently.

	Cheers,

	Matthew