Re: MD ROOT and image size limitation (makes kernel panic)


On Mon, May 16, 2011 at 11:36 AM, <rank1seeker@xxxxxxxxx> wrote:
I have a 4 GB or ram, so why kernel panic with my MD ROOT, if larger then
~40 MB?
I've tried to split up root in 20MB image and usr in 160 MB
Via loader.conf root becomes md0 and usr md1 and panic occurs even when
they are split

I had to get rid of md1, to be able to boot with md0 as a root.

What exactly imposes limitation, inside kernel's code to SIZE of an image?
My hardware definatelly isn't ...

Is this different on amd64?
I've tested this, only with i386.

We hit this problem at work and the solution was to increase NKPT.

If you are using -current then NKPT is already a kernel config option.
With 8.x you will need to modify <machine/pmap.h>.

Well ..., it looks like my 8.2 RELEASE src, has it, but ONLY for i386

# less /usr/src/sys/i386/conf/NOTES

# Number of initial kernel page table pages used for early bootstrap.
# This number should include enough pages to map the kernel, any
# modules or other data loaded with the kernel by the loader, and data
# structures allocated before the VM system is initialized such as the
# vm_page_t array. Each page table page maps 4MB (2MB with PAE).
options NKPT=31

So, that would be 124 MB for kernel and it's modules or other data loaded with the kernel by the loader (i.e; md image)
In those nums, md image has only about ~45 MB for itself.

Kernel itself and it's ..., needs ~80 MB

I'll build a custom kernel, for "lifting" md image ...

Domagoj Smolčić

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