Re: Does FreeBSD support sparse kernel crash dumps?


--- Peter Wemm <peter@xxxxxxxx> wrote:
On Friday 07 April 2006 12:47 pm, Paul Marciano
wrote:
Hello. I read a while back about someone working
on
supporting sparse kernel crash dumps (dumping only
the
active kernel pages to the dump device as opposed
to
all physical memory - for machines where the phys
mem
is greater than the dump dev space.)

Does anyone know the status of that project? Was
it
committed, or are there plans to commit it?

I have a working prototype as of last night. There
should be something
committable in the next week or two.

When I boot my 2GB machine and force a crash dump
from single user mode, the
fully debuggable vmcore file is in the 40-50MB
range. A busy machine with
12GB ram took about 150MB to dump.

There are still some things to work out. It was
written for the amd64 kernel,
but can be ported to i386.

-Peter



That's very timely news Peter. Do you think your code
is easily back-portable to 5.4? Are the changes
limited to dump_machdep.c or otherwise not dependent
on a great deal of -current updates?

Do you compress the data stream at all (e.g. gzip)?


I have a specific need on a CompactFlash based system.
I have a 256MB IDE mode card on a machine with 512MB
physical memory. I can probably commit 128MB of the
card as a dumpdev but I can't go beyond that.

Good luck with it.

Regards,
Paul.


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