Messages in this thread | | | From | Song Liu <> | Subject | Re: [PATCH v2 3/3] perf-stat: introduce config stat.bpf-counter-events | Date | Thu, 8 Apr 2021 18:08:20 +0000 |
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> 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 "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.
> >> >>> >>>> .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?
Thanks, Song
> > we can allow any event to be BPF-managed, right? IIUC we don't care, > the code will work with any event
Yes, the code works with any event.
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