My problems with stability on -current

[Alexander Motin]

On 11.05.2011 08:17, Doug Barton wrote:
> I had an interesting result doing nothing but switching from HPET to
> LAPIC ... no crash. Still on the same version of -current (r221566) the
> only thing I've done is to add kern.eventtimer.timer="LAPIC" to
> /boot/loader.conf, and so far I haven't been able to get it to crash no
> matter how much I compile, or how much other stuff I do in the
> background. I _can_ get the system heavily loaded enough so that the
> mouse can drag across the screen, windows take visible time to repaint,
> etc. That happens with a load average of 4+ on this core 2 duo. But
> other than that (which is not altogether unreasonable) the system has
> been very stable for a couple of days now.
>
> Does that suggest a next step in terms of what to test?

The fact that LAPIC is working fine can mean that problem is either HPET 
specific or non-per-CPU timers specific. To check that you could try to 
use i8254 timer in one-shot mode:
hint.attimer.0.timecounter=0
kern.eventtimer.timer="i8254"

, or use HPET in per-CPU mode:
hint.atrtc.0.clock=0
hint.attimer.0.clock=0
hint.hpet.X.legacy_route=1

But the most informative would be to see what's going on with HPET 
interrupts during the freezes. With HPET hardware it is very easy to 
loose interrupt. And the lost interrupt means problem for many things. 
There are some workarounds made for that, but I can't be sure. For that 
case you could experiment with  this patch:
--- acpi_hpet.c.prev    2010-12-25 11:28:45.000000000 +0200
+++ acpi_hpet.c 2011-05-11 14:30:59.000000000 +0300
@@ -190,7 +190,7 @@ restart:
                 bus_write_4(sc->mem_res, HPET_TIMER_COMPARATOR(t->num),
                     t->next);
         }
-       if (fdiv < 5000) {
+       if (1 || fdiv < 5000) {
                 bus_read_4(sc->mem_res, HPET_TIMER_COMPARATOR(t->num));
                 now = bus_read_4(sc->mem_res, HPET_MAIN_COUNTER);

-- 
Alexander Motin