svn commit: r212964 - head/sys/kern

[Pawel Jakub Dawidek]

On Fri, Sep 24, 2010 at 09:23:04AM -0400, John Baldwin wrote:
> > Because disks are big and (again, just trying to explain my
> > understanding of what I inherited) we want all the support
> > to be in place, just not turned on.  There is a difference
> > between "You can give us much better information by doing
> > <these extra installation steps, including installing the
> > .symbols goo> and then making a one-line change to rc.conf"
> > versus "You can give us much better information by making
> > a one-line change to rc.conf".
> 
> The biggest argument against this (and the reason I always enable crashdumps
> on all machines I am involved with) is that many panics are not easily
> reproducible, esp. ones that trigger under load.  If dumpdev is not on by
> default, then the info from a rare or hard-to-trigger bug may simply be lost.
> Also, "just send-pr or mail the 'foo' file" is even simpler than "enable this
> knob in rc.conf and reproduce your issue, then come back".

I am bigger fan of textdumps than minidumps, because in my opinion
textdumps provide quite a lot of useful info. I'm working with FreeBSD
kernel for years now and almost entirely avoided gdb for kernel
debugging. DDB and printf(9) are in 99% enough for me (maybe I'm too
traditional, but that's the fact). I'm not saying that textdumps are
enough in 99%, though.

> Well, if we turn it on we should document it clearly.  Folks are already
> interested in asking for help once a machine panics, and if the reply to a
> query on questions@ can say "please go look for a file named 'foo' and e-mail
> it somewhere or send-pr it", that is far simpler than having to enable dumps
> and reproduce the panic.

Another important thing in my opinion is privacy of user's data. Once
the data hit the disk it can stay there forever. This is why I use
encrypted swap everywhere. I'd never send kernel minidump from my
laptop or from any of my servers to anyone, but I'd be happy to send
textdump.

I find textdumps a great solution that's in the middle between
protecting user's privacy and providing a lot of useful info and I'd
much prefer to turn on textdumps by default and eventually extend what
we dump, than to make minidumps the default.

You can always ask user to add this one-line to rc.conf to turn
minidump on and provide you the info that was missing in textdump.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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