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Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter

From "Wangnan (F)" <wangnan0@huawei.com>
Newsgroups linux.kernel
Subject Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter
Date 2015-07-17 13:50 +0200
Message-ID <pNcjo-4ml-5@gated-at.bofh.it> (permalink)
References <pNbnk-31b-7@gated-at.bofh.it> <pNbnk-31b-27@gated-at.bofh.it> <pNbGG-3Dh-15@gated-at.bofh.it> <pNc9I-4aY-15@gated-at.bofh.it> <pNc9I-4aY-13@gated-at.bofh.it>
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On 2015/7/17 19:39, Peter Zijlstra wrote:
> On Fri, Jul 17, 2015 at 07:29:07PM +0800, Wangnan (F) wrote:
>>
>> On 2015/7/17 19:05, Peter Zijlstra wrote:
>>> On Fri, Jul 17, 2015 at 06:43:35PM +0800, kaixu xia wrote:
>>>> The function bpf_read_pmu() can get the specific map key, convert
>>>> the corresponding map value to the pointer to struct perf_event and
>>>> return the Hardware PMU counter value.
>>> Thanks for having me on Cc :/
>>>
>>>> Signed-off-by: kaixu xia <xiakaixu@huawei.com>
>>>> ---
>>>> +static u64 bpf_read_pmu(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
>>>> +{
>>>> +	void *value = (void *) (unsigned long) r1;
>>>> +	struct perf_event *event;
>>>> +	u64 count;
>>>> +
>>>> +	if (!value || !(*(unsigned long *)value))
>>>> +		return 0;
>>>> +
>>>> +	event = (struct perf_event *)(*(unsigned long *)value);
>>>> +
>>>> +	if (event->state == PERF_EVENT_STATE_ACTIVE)
>>>> +		event->pmu->read(event);
>>>> +
>>>> +	count = local64_read(&event->count);
>>>> +
>>>> +	return count;
>>>> +}
>>> Hell no, that's way broken.
>> What about calling perf_event_read_value() then?
> Depends on what all you need, if you need full perf events to work then
> yes perf_event_read_value() is your only option.
>
> But note that that requires scheduling, so you cannot actually use it
> for tracing purposes etc..
What you mean "full perf events"? Even with your code some event still 
not work?

Thank you.

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[RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter kaixu xia <xiakaixu@huawei.com> - 2015-07-17 12:50 +0200
  Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 13:10 +0200
    Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 13:40 +0200
    Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 13:40 +0200
      Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter "Wangnan (F)" <wangnan0@huawei.com> - 2015-07-17 13:50 +0200
        Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 14:00 +0200
          Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 14:00 +0200
            Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter "Wangnan (F)" <wangnan0@huawei.com> - 2015-07-17 14:10 +0200
              Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter "Wangnan (F)" <wangnan0@huawei.com> - 2015-07-17 14:10 +0200
              Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 14:20 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter "Wangnan (F)" <wangnan0@huawei.com> - 2015-07-17 14:40 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 14:50 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 14:50 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter pi3orama <pi3orama@163.com> - 2015-07-17 15:10 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 15:30 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter pi3orama <pi3orama@163.com> - 2015-07-17 15:50 +0200
    Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter "Wangnan (F)" <wangnan0@huawei.com> - 2015-07-17 13:40 +0200

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