On Mon, Sep 01, 2014 at 09:27:17AM +0300, Adrian Hunter wrote: > On 08/30/2014 11:53 AM, Jiri Olsa wrote: > > On Fri, Aug 29, 2014 at 09:48:51PM +0300, Adrian Hunter wrote: > >> On 16/07/2014 9:22 p.m., Jiri Olsa wrote: > >>> On Wed, Jul 16, 2014 at 06:04:44PM +0300, Adrian Hunter wrote: > >>>> On 16/07/2014 5:25 p.m., Jiri Olsa wrote: > >>>>> On Mon, Jul 14, 2014 at 01:02:44PM +0300, Adrian Hunter wrote: > >>>>>> This enables a PMU event to be specified in the form: > >>>>>> > >>>>>> pmu// > >>>>>> > >>>>>> which is effectively the same as: > >>>>>> > >>>>>> pmu/config=0/ > >>>>>> > >>>>>> This patch is a precursor to defining > >>>>>> default config for a PMU. > >>>>> > >>>>> I understand the need for default config, but could you please elaborate > >>>>> why do we want to parse 'pmu//' as an event string string? > >>>> > >>>> Currently the parser requires the slashes to identify a PMU event > >>>> as opposed to a hardware or other kind of event. > >>> > >>> right, so why do we want to parse 'pmu//' as an event string? ;-) > >> > >> I am not sure what you mean. Here I am using 'pmu' as a placeholder > >> for a real PMU name. So actual event strings are 'intel_bts//' or > >> 'intel_pt//' or 'intel_pt/tsc=0,noretcomp=1/' > > > > so the consequence of default arguments is that you can > > specify event just by the pmu name, like: > > -e intel_pt// > > > > which means (with default attributes): > > -e intel_pt/tsc=1,noretcomp=0/ > > > > I guess I wanted to hear more elaboration why is this better > > than the current way we have by defining an alias, like: > > > > krava alias: "tsc=1,noretcomp=0" > > > > -e intel_pt/krava/ > > > > which gives the same result > > The default value must be provided by perf tools not the kernel e.g. > an older version of perf tools will not be aware of new hardware > features that the kernel may know about. If the kernel enables > new features by default then the tool may fail. Thus the default > value has to be under the control of the tools not the kernel, so > a sysfs alias will not work. >
I dont follow, could u provide some example? why the tool needs to understand.. it will just take the alias and apply/use it? The alias follows the format logic, which tells how to apply values on perf_event_attr.. and the kernel knows best what's supported in its version.. jirka -- 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/
