Does FreeBSD support sparse kernel crash dumps?

Peter Wemm peter at
Fri Apr 7 22:20:27 UTC 2006

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.


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