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Date: Mon, 29 Mar 2010 15:20:57 +0100 From: Stephane Eranian <eranian@...gle.com> To: Peter Zijlstra <peterz@...radead.org> Cc: mingo@...e.hu, Linus Torvalds <torvalds@...l.org>, linux-kernel@...r.kernel.org Subject: Re: [RFC,PATCH 2/2] perf, x86: Utilize the LBRs for machine/oops debugging On Mon, Mar 29, 2010 at 3:13 PM, Peter Zijlstra <peterz@...radead.org> wrote: > On Mon, 2010-03-29 at 13:47 +0100, Stephane Eranian wrote: >> On Mon, Mar 29, 2010 at 1:20 PM, Peter Zijlstra <a.p.zijlstra@...llo.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(). >> > >> >> When this is enabled, it will prevent changing the LBR configuration to >> record only selected branches. Unless you are willing to accept filtered >> content in the kernel dump. > > Sure, but since we don't support that silly config reg anyway that's > pretty much not an issue ;-) > I will provide a patch to make it available. This is needed for certain measurements. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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