Re: diskless sparc locks up under memory pressure

[Chuck Silvers <chuq%chuq.com@localhost>]

On Mon, Nov 09, 2020 at 11:21:56AM +1100, Paul Ripke wrote:
> On Sat, Nov 07, 2020 at 06:33:26PM +0300, Valery Ushakov wrote:
> > I've upgraded my Krups (64MB RAM, diskless) to 9.99.75 as of Nov 6 and
> > the machine is locking up at boot time in rc.d/fccache.  If I disable
> > fccache in rc.conf it boots but then eventually locks up when
> > makemandb is run.  The machine doesn't respond to pings, etc, but can
> > enter ddb.  In all cases the ddb stacktrace goes through:
> > 
> > ...
> > uvm_fault_internal
> > mem_access_fault4m
> > memfault_sun4m
> > copyout
> > 
> > with the top part of the stack trace varying.
> 
> I reported something similar with amd64 back in May:
> 
> https://mail-index.netbsd.org/current-users/2020/05/02/msg038498.html
> 
> If I get a chance, I'll re-test that and see if it still locks up.

I have the same questions for both of you:

could you give some examples of what the rest of the stack has?

what's the stack trace for the pagedaemon thread?

try printing the UVM activity counters in ddb with "show uvmexp",
then continue from ddb and wait 10 seconds, then print the counters again.
by looking at which counters change we can see what (if anything)
the pagedaemon is doing to try to free up some memory.

what's the state of the relevant pools for network activity,
such as mc_cache and mcl_cache, and do those change over time?
you can print these from ddb with "show pool *mb_cache" and
"show pool *mcl_cache".

-Chuck