Messages in this thread | | | Date | Mon, 29 Mar 2010 19:02:59 +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 <a.p.zijlstra@chello.nl> wrote:
> The LBRs are relatively cheap to keep enabled and provide some history to > OOPSen, also some CPUs are reported to keep them over soft-reset, which > allows us to use them to debug things like tripple faults. > > Therefore introduce a boot option: lbr_debug=on, which always enable the > LBRs and will print the LBRs on CPU init and die().
Yummie!
Have you got some sample lbr_debug=1 output as well by any chance, with a crash provoked somewhere? How good is the output in practice? (i.e. how many artificial entries do we have at the end of the buffer, filled with crash related addresses?)
Also, i think we should use something more descriptive than lbr_debug=y. Perhaps crash_trace=1 or so?
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.
Ingo
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