On 01/07/15 11:19, Adrian Hunter wrote: > On 30/06/15 16:23, Adrian Hunter wrote: >> On 30/06/15 13:56, Ingo Molnar wrote: >>> >>> * Adrian Hunter <adrian.hun...@intel.com> wrote: >>> >>>>> Yeah, so I did a 'newbie test': >>>>> >>>>> I pulled the tree and saw that it has a >>>>> tools/perf/Documentation/intel-bts.txt >>>>> file and started reading it. >>>>> >>>>> Based on its text: >>>>> >>>>> The Intel BTS kernel driver creates a new PMU for Intel BTS. The perf >>>>> record >>>>> option is: >>>>> >>>>> -e intel_bts// >>>>> >>>>> Currently Intel BTS is limited to per-thread tracing so the >>>>> --per-thread option >>>>> is also needed. >>>>> >>>>> I tried the following command which failed: >>>>> >>>>> triton:~/tip> perf record -e intel_bts// --per-thread sleep 1 >>>>> invalid or unsupported event: 'intel_bts//' >>>>> Run 'perf list' for a list of valid events >>>>> >>>>> usage: perf record [<options>] [<command>] >>>>> or: perf record [<options>] -- <command> [<options>] >>>>> >>>>> -e, --event <event> event selector. use 'perf list' to list >>>>> available events >>>>> >>>>> That's a really ... unhelpful message. If I typoed something I want to >>>>> know that. >>>>> If the kernel does not support something, I want to know about that too. >>>>> Tooling >>>>> telling me: "maybe you typoed something, maybe it's not supported, I >>>>> really don't >>>>> care" is not very productive. >>>> >>>> That is not entirely true. The message says "Run 'perf list' for a list of >>>> valid >>>> events" which will tell you if the event is valid. So you can tell the >>>> difference between a typo and unsupported event. >>> >>> Yeah, but my point is: why doesn't the tool do this disambiguation for me? >>> Tools >>> are hard enough to use as-is already, no need to put artificial roadblocks >>> in the >>> path of first time users. >> >> That applies to all events e.g. >> >> # perf record -e sched:sched_swotch sleep 1 >> invalid or unsupported event: 'sched:sched_swotch' >> >> Run 'perf list' for a list of valid events >> >> >> >> usage: perf record [<options>] [<command>] >> >> or: perf record [<options>] -- <command> [<options>] >> >> >> >> -e, --event <event> event selector. use 'perf list' to list available >> events >> >> So it is a general problem. >> >>> >>>>> So this was with a distro kernel, and in the hope that I'm missing some >>>>> magic >>>>> new kernel feature, I tried it the latest -tip kernel, but it still gives >>>>> me >>>>> the same failure. >>>>> >>>>> So the test newbie user got stuck after wasting some time. >>>>> >>>>> Me as a kernel developer could probably figure it out, but that's not the >>>>> point: if newbies cannot discover and use our new features then it's as >>>>> if >>>>> they didn't exist, and I'm not pulling non-existent features! ;-) >>>>> >>>>> Could we please improve all this? >>>> >>>> 'perf list' shows the event wasn't supported, so I am not sure what more >>>> the >>>> "newbie" could expect. Do you have any suggestions? >>> >>> So I think a first time user would expect a clear message from the >>> computer: what >>> was wrong with what he wrote and what should he do to fix it. >>> >>> Btw., here's the 'perf list' output from a system running the latest -tip >>> kernel: >>> >>> vega:~> uname -a >>> Linux vega 4.1.0-02935-g390ad45394a3-dirty #567 SMP PREEMPT Mon Jun 29 >>> 11:44:48 CEST 2015 x86_64 x86_64 x86_64 GNU/Linux >>> vega:~> perf list | grep -i bts >>> vega:~> >>> >>> so is there any kernel feature dependency? It's unclear. If yes, it should >>> be >>> mentioned in the document, and in the tooling output as well. If not then >>> we have >>> a bug somewhere. >> >> I am not aware of any dependencies, apart from perf events itself. >> >> Are you sure you compiled perf tools with the new patches ;-) >> And it is an Intel CPU? >>
I am going to need to know what hardware it is and cpu feature flags i.e. /proc/cpuinfo Also ls /sys/bus/event_source/devices -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
