Hi,

I cannot boot a very recent build (minutes ago) of 8-CURRENT on VMWare=20

Server. Panic ("integer divide fault" - is this division by zero?) is in =
sched_rr_interval().
More info here:

http://ivoras.sharanet.org/stuff/panic/
It might be because I'm trying to run without WITNESS+INVARIANTS.

No, building a GENERIC kernel doesn't change anything. It's also not a=20

cvsup glitch - todays sources panic in exactly the same way.

Can you tell me what the values of:
sysctl kern.sched.slice
and
sysctl kern.clockrate
are?
Thanks,

Jeff

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The machine doesn't finish booting the kernel (i.e. init isn't executed) =
and fetching sysctls apparently isn't supported by the kernel debugger=20

(though it would be nice if it did work, at least for simple variables).
The only old kernel I have is 7.0RC1, and in it I can only access=20

kern.clockrate, which is { hz=3D50, tick=3D20000, profhz=3D33, stathz=3D6=

 }.
Since you brought up the issue of clocks, I removed the tuning of=20

kern.hz (it was present there practically forever) and the panic's gone. =
I use low values for kern.hz in VMWare to (noticably) reduce problems=20

with clock drift and context switches, so it would be nice to not have=20

the kernel panic with it :)
Apparently lowering kern.hz works upto about 75 - anything lower=20

triggers the integer divide fault.

I ran into this problem recently.  It appears that sched_slice is set

to zero when realstathz drops below 10 in sched_ule.c:
  	sched_slice = (realstathz/10);	/* ~100ms */
I was able to work around the problem with the following patch.  The

image no longer panics, but I have not done any stress or performance

testing.  Is there a better solution to this problem?
For reference:
 > uname -a

FreeBSD vm7.vadev.org 7.0-STABLE FreeBSD 7.0-STABLE #3 r50:55M: Mon

Jul 28 09:27:04 EDT 2008     root@vm7.vadev.org:/usr/obj/usr/src/sys/

VMWARE  i386

 > sysctl -a | grep kern.clock

kern.clockrate: { hz = 50, tick = 20000, profhz = 33, stathz = 6 }
The patch is against 7-STABLE from 7/24/2008.
Thanks.
- Ben
Index: src/sys/kern/sched_ule.c

===================================================================

--- src/sys/kern/sched_ule.c	(revision 53)

+++ src/sys/kern/sched_ule.c	(working copy)

@@ -1325,6 +1325,7 @@

  	 */

  	realstathz = hz;

  	sched_slice = (realstathz/10);	/* ~100ms */

+	sched_slice = sched_slice ? sched_slice : 1;

  	tickincr = 1 << SCHED_TICK_SHIFT;
  	/* Add thread0's load since it's running. */

@@ -1345,6 +1346,7 @@
  	realstathz = stathz ? stathz : hz;

  	sched_slice = (realstathz/10);	/* ~100ms */

+	sched_slice = sched_slice ? sched_slice : 1;
  	/*

  	 * tickincr is shifted out by 10 to avoid rounding errors due to
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