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Date:      Mon, 10 Dec 2001 18:39:50 -0500 (EST)
From:      Andrew Gallatin <gallatin@cs.duke.edu>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        John Baldwin <jhb@FreeBSD.org>, freebsd-arch@FreeBSD.org
Subject:   Re: Proposed auto-sizing patch to sysinstall (was Re: Using a la
Message-ID:  <15381.18374.269597.931300@grasshopper.cs.duke.edu>
In-Reply-To: <200112102221.fBAMLD648896@apollo.backplane.com>
References:  <XFMail.011210133843.jhb@FreeBSD.org> <200112102221.fBAMLD648896@apollo.backplane.com>

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Matthew Dillon writes:
 > 
 >     In regards to the "dump" being smarter... system core dump is only
 >     a dump of physical memory.  It does not dump VM Objects.  Of course,
 >     it does wind up dumping whatever is in physical memory, such as the
 >     file cache, but it's important that it do so or we kernel hackers
 >     would have a hard time tracking problems down.  Also, you don't want

I think you're one of the few people who might actually care about the
contents of the buffercache.  That's why it would be optional.

 >     to make a system core dump too 'smart'... the system could be in a
 >     very corrupted state when dumping so we can't safely traverse dozens of
 >     system structures.

True, but in nearly three years of using partial dumps, I can't
remember that ever happening.  And I was mucking with the VM system
in my zero-copy work.  Again, that's why it would be optional.

Anyway, have a look at the partial dump diffs done 2 years ago by
Darrell Anderson.
http://www.cs.duke.edu/~anderson/freebsd/partialdump
These are old, non-context diffs to 4.0 (at the time -current).
There'd be some mergework to do, but I think it would be quite handy.


Drew

PS: We eventually abandoned partial dump in favor of netdump, which works
on roughly the same principals but is quite a bit faster, but more of
a local hack: http://www.cs.duke.edu/~anderson/freebsd/netdump/






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