Messages in this thread | | | Date | Thu, 8 Apr 2021 20:24:47 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH v2 3/3] perf-stat: introduce config stat.bpf-counter-events |
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On Thu, Apr 08, 2021 at 06:08:20PM +0000, Song Liu wrote: > > > > On Apr 8, 2021, at 10:45 AM, Jiri Olsa <jolsa@redhat.com> wrote: > > > > On Thu, Apr 08, 2021 at 05:28:10PM +0000, Song Liu wrote: > >> > >> > >>> On Apr 8, 2021, at 10:20 AM, Jiri Olsa <jolsa@redhat.com> wrote: > >>> > >>> On Thu, Apr 08, 2021 at 04:39:33PM +0000, Song Liu wrote: > >>>> > >>>> > >>>>> On Apr 8, 2021, at 4:47 AM, Jiri Olsa <jolsa@redhat.com> wrote: > >>>>> > >>>>> On Tue, Apr 06, 2021 at 05:36:01PM -0700, Song Liu wrote: > >>>>>> Currently, to use BPF to aggregate perf event counters, the user uses > >>>>>> --bpf-counters option. Enable "use bpf by default" events with a config > >>>>>> option, stat.bpf-counter-events. This is limited to hardware events in > >>>>>> evsel__hw_names. > >>>>>> > >>>>>> This also enables mixed BPF event and regular event in the same sesssion. > >>>>>> For example: > >>>>>> > >>>>>> perf config stat.bpf-counter-events=instructions > >>>>>> perf stat -e instructions,cs > >>>>>> > >>>>> > >>>>> so if we are mixing events now, how about uing modifier for bpf counters, > >>>>> instead of configuring .perfconfig list we could use: > >>>>> > >>>>> perf stat -e instructions:b,cs > >>>>> > >>>>> thoughts? > >>>>> > >>>>> the change below adds 'b' modifier and sets 'evsel::bpf_counter', > >>>>> feel free to use it > >>>> > >>>> I think we will need both 'b' modifier and .perfconfig configuration. > >>>> For systems with BPF-managed perf events running in the background, > >>> > >>> hum, I'm not sure I understand what that means.. you mean there > >>> are tools that run perf stat so you don't want to change them? > >> > >> We have tools that do perf_event_open(). I will change them to use > >> BPF managed perf events for "cycles" and "instructions". Since these > >> tools are running 24/7, perf-stat on the system should use BPF managed > >> "cycles" and "instructions" by default. > > > > well if you are already changing the tools why not change them to add > > modifier.. but I don't mind adding that .perfconfig stuff if you need > > that > > The tools I mentioned here don't use perf-stat, they just use > perf_event_open() and read the perf events fds. We want a config to make
just curious, how those tools use perf_event_open?
> "cycles" to use BPF by default, so that when the user (not these tools) > runs perf-stat, it will share PMCs with those events by default.
I'm sorry but I still don't see the usecase.. if you need to change both tools, you can change them to use bpf-managed event, why bother with the list?
> > > >> > >>> > >>>> .perfconfig makes sure perf-stat sessions will share PMCs with these > >>>> background monitoring tools. 'b' modifier, on the other hand, is useful > >>>> when the user knows there is opportunity to share the PMCs. > >>>> > >>>> Does this make sense? > >>> > >>> if there's reason for that then sure.. but let's not limit that just > >>> on HARDWARE events only.. there are RAW events with the same demand > >>> for this feature.. why don't we let user define any event for this? > >> > >> I haven't found a good way to config RAW events. I guess RAW events > >> could use 'b' modifier? > > any event uing the pmu notation like cpu/instructions/ > > Can we do something like "perf config stat.bpf-counter-events=cpu/*" means > all "cpu/xx" events use BPF by default?
I think there's misundestanding, all I'm saying is that IIUC you check events stat.bpf-counter-events to be HARDWARE type, which I don't think is necessary and we can allow any event in there
jirka
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