Strange ARC/Swap/CPU on yesterday's -CURRENT

[Justin Hibbits]

On Fri, Apr 6, 2018 at 10:25 AM, Justin Hibbits <chmeeedalf at gmail.com> wrote:
> On Fri, Apr 6, 2018 at 10:08 AM, Mark Johnston <markj at freebsd.org> wrote:
>> On Fri, Apr 06, 2018 at 12:47:14AM +0000, Justin Hibbits wrote:
>>> My powerpc64 embedded machine is virtually unusable since these vm changes.
>>> I tried setting vfs.zfs.arc_free_target as suggested, and that didn't help
>>> at all. Eventually the machine hangs and just gets stuck in vmdaemon, with
>>> many processes in wait channel btalloc.
>>
>> You don't really have the same symptoms that Don is reporting.
>
> Okay.  I latched onto the thread because it seemed similar.
>
>> Threads being stuck in btalloc implies a KVA shortage. So:
>> - What do you mean by "stuck in vmdaemon"?
>
> The machine hangs, and my ssh sessions get killed.  I can't do
> anything at the console except break into kdb.  When I do, the running
> thread is always vmdaemon.
>
>> - Which commits specifically cause problems? Does reverting r329882 fix the
>>   hang?
>
> I'll try reverting it and report back.  Thankfully I can buildkernel
> successfully on the machine before it hangs.  Can't do more than that,
> though.

I reverted back to r329881, and successfully built world.  Updated to
r329882 and it got stuck with processes in btalloc.

I've seen other reports of r329882 causing problems on powerpc64 as
well, with other bizarre behaviors.


- Justin