From owner-freebsd-questions  Wed Jul 22 20:11:01 1998
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To: Jaspal Kohli <jaspal@best.com>
cc: freebsd-questions@FreeBSD.ORG
Subject: Re: compact kernel dumps 
In-reply-to: Your message of "Wed, 22 Jul 1998 10:00:39 PDT."
             <35B61AB6.4B818B9B@best.com> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Wed, 22 Jul 1998 20:09:29 -0700
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>I am running a 2.2.5 base on a PII system with 512MB of memory.  With
>the
>large memory configuration, the dump takes a while (a few minutes) and I
>
>need to reserve a significant amount of disk space in /var/crash (the
>compression helps, but is not predictable).
>
>Has anyone worked on making the kernel dump more compact by limiting it
>to
>pages used by the kernel and interesting in analyzing kernel problems?
>
>Any suggestions on to how to efficiently determine these set of pages
>with the
>VM implementation in 2.2.5?

   Possible, but quite difficult. You'd first need to define a new crash
dump format, then write code to examine the kernel page tables and write
out the relevant pages in this new format. Then you'd need to write code
(changes to savecore and gdb) to read/parse it all after the system came
back up. While you're at it, I'd like to see a general purpose crash dump
analyzer that provides lots of useful data to us developers from people's
crash dumps.

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project

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