Re: -CURRENT kernel panic

On Sun, 7 Mar 2004, Andre Guibert de Bruet wrote:

> On Sat, 6 Mar 2004, Vincent Poy wrote:
> > On Sat, 6 Mar 2004, Vincent Poy wrote:
> > > 	It seems to do it on the dump of /usr and restoring to /mnt/usr.
> > > I have tried the following but they panic the kernel as soon as the memory
> > > size is displayed.
> > >
> > > added to kernel config:
> > > options         VM_KMEM_SIZE_MAX=(768*1048576)
> > > options         VM_KMEM_SIZE_SCALE=2
> > >
> > > Tried it on a kernel without the above but added in /boot/loader.conf
> > >
> > > vm.kmem_size=429391872
> > >
> > > and they both crashed at the same spot as well...
> > >
> > > CPU: Mobile Intel(R) Pentium(R) 4 - M CPU 2.60GHz (2592.36-MHz 686-class CPU)
> > >   Origin = "GenuineIntel"  Id = 0xf29  Stepping = 9
> > >
> > > Features=0xbfebf9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV,P
> > > AT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
> > > real memory  = 2147360768 (2047 MB)
> > > avail memory = 2095669248 (1998 MB)
> > >
> > > 	Any ideas how to fix this?
> >
> > 	I managed to get the system not panicing on bootup if I set the
> > VM_KMEM_SIZE_MAX to 384MB.  At 512MB and 768MB, it would panic but anyone
> > knows what the default VM_KMEM_SIZE_MAX size is?
>
> That's the maximum amount of KMEM that your system can have. Let's say for
> example that you have a system with 4GB of RAM. You set VM_KMEM_SIZE_MAX
> to 1GB but VM_KMEM_SIZE_SCALE to 8 you get:
>
> VM_KMEM_SIZE_MAX: 1024 MB of KMEM
> VM_KMEM_SIZE_SCALE: 512 MB of KMEM (4096/8)
>
> The algorithm uses the lesser of these two numbers. Remember that a whole
> lot of things use the allocated memory so don't skimp! If you don't want
> to use the memory in your system, take it out and set it on the desk. ;-)

	Okay, here's a dumb question.  If it uses the less of the two
numbers, is there a reason to need to even define the VM_KMEM_SIZE_SCALE
since wouldn't by default, it be 1/3rd of your RAM anyways?

> I've found through personal experience and endless hours of experimenting
> on fairly busy machines that the following values work for the various RAM
> configurations (Lower values may also work depending upon disk, net and
> load):
>
> RAM		KMEM size
> 4.0GB		768MB
> 3.5GB		768MB
> 3.0GB		512MB
> 2.5GB 		384MB
> 2.0GB		384MB
> 1.5GB and below	256MB

	You're right that anything above 384MB using a scale of 2, the
kernel would panic as soon as the Real Memory is posted in the boot.  Did
this problem actually exist recently because prior to February 28, I was
on a September 26, 2003 -CURRENT and it has not had the problem.  I'm
using maxusers=512 in the kernel as well as 65536 NMBCLUSTERS, it used to
be 32768 but I thought that was what was causing the panic.

> As with everything, backup your data, put on your fire-retarding suit, and
> YMMV. :-)

	Nah, the kernel one doesn't require backing up the data since the
only reason I get the panic is because I'm dumping both / and /usr to
another identical drive.  It's only doing the /boot/loader.conf variable
for kmem that's scary. ;)


Cheers,
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