Does FreeBSD support sparse kernel crash dumps?
pm940 at yahoo.com
Fri Apr 7 23:01:53 UTC 2006
--- Peter Wemm <peter at wemm.org> wrote:
> On Friday 07 April 2006 12:47 pm, Paul Marciano
> > Hello. I read a while back about someone working
> > supporting sparse kernel crash dumps (dumping only
> > active kernel pages to the dump device as opposed
> > all physical memory - for machines where the phys
> > is greater than the dump dev space.)
> > Does anyone know the status of that project? Was
> > 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.
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.
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