> On Apr 8, 2021, at 10:45 AM, Jiri Olsa <jo...@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 <jo...@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 <jo...@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.
