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Date: Sat, 7 Nov 2015 09:59:57 +0530 From: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com> To: Peter Zijlstra <peterz@...radead.org>, Michael Ellerman <mpe@...erman.id.au> Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, Stephane Eranian <eranian@...il.com>, Russell King <linux@....linux.org.uk>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com> Subject: Re: [RFC PATCH 0/3]perf/core: extend perf_reg and perf_sample_regs_intr On Friday 06 November 2015 03:55 PM, Peter Zijlstra wrote: > On Fri, Nov 06, 2015 at 09:04:00PM +1100, Michael Ellerman wrote: >> It's a perrenial request from our hardware PMU folks to be able to see the raw >> values of the PMU registers. >> >> I think partly it's so that they can verify that perf is doing what they want, >> and some of it is that they're interested in some of the more obscure info that >> isn't plumbed out through other perf interfaces. >> >> We've used various internal hacks over the years to keep them happy. This is an >> attempt to use a somewhat standard mechanism. >> >> It would also be helpful for those of us working on the perf hardware backends, >> to be able to verify that we're programming things correctly, without resorting >> to debug printks etc. >> >> Basically we want to sample regs at the time of the perf interrupt, so we >> though PERF_SAMPLE_REGS_INTR made senes :) >> >> But if you think this is the wrong mechanism within perf, then please let us >> know. >> >> I know perf's mission is to abstract as much of the arcane hardware details >> into a generic interface and make PMUs actually useful for normal folks, and we >> are committed to that, but it would also be useful to be able to get the raw >> values for a different type of user. >> >> Maddy's patch only exports PMC1-6 and MMCR0/1. I think we also need to export >> some others, in particular MMCRA has a lot of stuff in it, half of which is not >> even architected. So that would have to be exported as "POWER8_MMCRA". And then >> there's the SIAR/SDAR/SIER which contain a bunch of info on sampled >> instructions that is not currently plumbed out. > OK, no objections then. But this is useful information and should be > included in the patch set. > Sure. Will add the information in the next version. Maddy -- 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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