On Friday 06 November 2015 03:34 PM, Michael Ellerman wrote: > On Fri, 2015-11-06 at 10:24 +0100, Peter Zijlstra wrote: >> On Fri, Nov 06, 2015 at 12:57:17PM +0530, Madhavan Srinivasan wrote: >>> On Thursday 05 November 2015 06:37 PM, Peter Zijlstra wrote: >>>> On Thu, Nov 05, 2015 at 02:16:15AM +0530, Madhavan Srinivasan wrote: >>>>> Second patch updates struct arch_misc_reg for arch/powerpc with pmu >>>>> registers >>>>> and adds offsetof macro for the same. It extends perf_reg_value() >>>>> to use reg idx to decide on struct to return value from. >>>> Why; what's in those regs? >>> Was out and did not have access to mail, so missed to respond in time. >>> >>> In current implementation of patch 2, have added >>> few pmu control/status and counter registers, >>> which give additional information about the PMU context >>> for the sample. >> Yes, I saw that, you still haven't answered the question though. What is >> in those regs? Why is exposing that information like this the best >> option. > 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.
Sure. I will rework the patch to include the other regs also. Maddy > > cheers > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
