Re: swap_pager: cannot allocate bio

> On Nov 12, 2021, at 14:52, Warner Losh <imp@bsdimp.com> wrote:
> My swap is on a partition on the non-ZFS disk.  A physical disk as far as the kernel knows, hardware RAID1.
> 
> # pstat -s
> Device           1K-blocks   Used    Avail  Capacity
> /dev/da0p3      445682648 1018524 444664124 0%
> 
> OK. That's well supported and should work w/o some of the issues that I raised. I'd misunderstood and thought you were swapping to zvols...
>  
> Let me know if what you’re saying above is true to my case, and any advice as to how I can avoid it.  I had a “not enough swap space” a while back, and accordingly increased the size of my swap partition.  I have 128GB of memory, though between the ARC and the big process I was running, that fills it easily.
> 
> Yea, this is a 'memory is exhausted' problem, and more swap won't help that. It's unclear why we run out so fast, and why the separate zones for the bio isn't providing a good level of insulation from out of memory scenarios.

Okay.  Well, I can’t easily add more memory to this machine, though I am investigating it.  I certainly can’t do it in short order.  I presume the problem is that I recently increased the size of this pool by adding a large raidz vdev to it.  I’ve only been seeing this since.  Is there any way I can “limit” the perceived size of the ZFS filesystem to ease the problem?  Is there anything I can tune to help?  Can I turn off or drastically reduce the ARC?  A decrease in performance would be better than getting stuck after a day or so.  :-)

                 - Chris