Messages in this thread | | | Date | Fri, 2 Apr 2010 22:44:46 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC,PATCH 2/2] perf, x86: Utilize the LBRs for machine/oops debugging |
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* Peter Zijlstra <peterz@infradead.org> wrote:
> On Mon, 2010-03-29 at 19:02 +0200, Ingo Molnar wrote: > > > Plus, it would be nice to have a sysctl entry for this as well - so that > > production systems can enable this if they want to enrich the output of > > some difficult-to-analyze kernel crash, without yet another reboot. > > Right, could do, but once it crashed it clearly to late to enable anything > ;-)
No. What i mean is that with your patch, a debugging session would go like this:
< kernel crashes > # reboot #1
< admin logs in and scratches head > < admin consults kernel hackers and enables lbr_debug=1 in /etc/grub.conf >
< admin reboots > # reboot #2
< kernel crashes again > # reboot #3
With the sysctl we'd have one reboot less:
< kernel crashes > # reboot #1
< admin logs in and scratches head > < admin consults kernel hackers and tweaks /proc/sys/kernel/x86/lbr_debug >
< kernel crashes again > # reboot #2
Thanks,
Ingo
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