Subject: Re: Possible serious bug in NetBSD-1.6.1_RC2
To: Brian Buhrow <>
From: Greg Oster <>
List: current-users
Date: 03/11/2003 14:13:04
Brian Buhrow writes:
> 	Hello Greg.  If I understand your message correctly, then I have a
> couple of questions and observations.
> 1.  According to sysctl, nkmempages is already at 8102.  This is about 33MB
> of memory, if my calculations are correct.  Using the value 8192 would be
> about 35MB of memory,not much more than is currently in use.  Is there a
> limit to the number of pages I can allocate?  Must it be a power of 2? 

Hmmmmm... On a machine w/ 512MB RAM I see:

oster@merlin-39> sysctl -a | grep kmem
vm.nkmempages = 32739

On one with 256MB RAM, I get:
cs# sysctl -a | grep kmem
vm.nkmempages = 16354

So maybe try 16384 instead of 8192?  (I would have though 8192 should have 
been more than sufficient tho!!)  I'm not sure what the limits are, nor whether
the values need to be a power of two or not.

>  In
> case it helps with the sizing, right now, under normal operation, the
> machine lasts 28-36 hours before it hangs or panics.  If I perform the
> exercise I listed in the previous e-mail, it hangs immediately.

I'll try to dig up some time this evening to try to reproduce the problem on 
my test box. (It only has 128MB RAM too...)  It's sounding like it's seen
mostly (exclusively?) when swap is on a RAID 5 set.

> 2.  I'm notcertain, but my guess is that the reason raid5 works under 1.5R
> and not 1.6 is not so much due to the changes in raidframe itself, but,
> rather, changes in the way kernel memory is managed by uvm.  They may be
> only tuning changes, but something definitely changed.

That sounds suspiciously correct... (depending on how some dynamic kernel 
memory allocation might be, it could be that the RAID driver exhausts kernel
memory when trying to page out stuff...  I need to do some testing it seems...)


Greg Oster