From: Ingo Molnar <mingo@elte.hu>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@osdl.org>,
linux-kernel@vger.kernel.org,
Stephane Eranian <eranian@google.com>
Subject: Re: [RFC,PATCH 2/2] perf, x86: Utilize the LBRs for machine/oops debugging
Date: Mon, 29 Mar 2010 19:02:59 +0200 [thread overview]
Message-ID: <20100329170259.GA15083@elte.hu> (raw)
In-Reply-To: <20100329122138.848413757@chello.nl>
* 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
next prev parent reply other threads:[~2010-03-29 17:03 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-29 12:20 [PATCH 0/2] perf: Use LBR for machine/oops debugging Peter Zijlstra
2010-03-29 12:20 ` [PATCH 1/2] perf, x86: fix __initconst vs const Peter Zijlstra
2010-03-29 12:20 ` [RFC,PATCH 2/2] perf, x86: Utilize the LBRs for machine/oops debugging Peter Zijlstra
2010-03-29 12:47 ` Stephane Eranian
2010-03-29 14:13 ` Peter Zijlstra
2010-03-29 14:20 ` Stephane Eranian
2010-03-29 17:02 ` Ingo Molnar [this message]
2010-03-29 17:12 ` Peter Zijlstra
2010-04-02 20:44 ` Ingo Molnar
2010-03-29 13:08 ` [PATCH 0/2] perf: Use LBR " Andi Kleen
2010-03-29 13:16 ` Stephane Eranian
2010-03-29 14:14 ` Peter Zijlstra
2010-03-29 20:09 ` Andi Kleen
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