Messages in this thread | | | Subject | Re: [PATCH 10/48] perf tools: Introduce bpf-output event | From | "Wangnan (F)" <> | Date | Wed, 24 Feb 2016 13:03:40 +0800 |
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On 2016/2/24 12:03, Wangnan (F) wrote: > > > On 2016/2/24 10:04, Wangnan (F) wrote: >> >> >> On 2016/2/24 9:58, Wangnan (F) wrote: >>>
[SNIP]
>>> So, there is something strange here: >>>> >>>> if (unlikely(event->oncpu != smp_processor_id())) >>>> return -EOPNOTSUPP; >>>> >>> >> >> All failures have 'event->oncpu == -1' here. I guess we should >> suppress warning in >> this case. But why event->oncpu becomes -1? >> > > For this specific test it is not surprising to see these error > messages. In this test > we create bpf-output channel on 'ls' process only, but the BPF script > is triggered > on all procs (BPF triggering is not related to perf event scheduling). > Trying to > output data through 'ls' specific bpf-output channel should fail if > this 'sys_write' > is not issued by 'ls' or its children. So it is a correct behavior. > > However, I also see them in system wide channel: > > # echo "" > /sys/kernel/debug/tracing/trace > # ./perf record -a -e bpf-output/no-inherit,name=evt/ \ > -e ./test_bpf_output.c/map:channel.event=evt/ > -a > ^C[ perf record: Woken up 0 times to write data ] > [ perf record: Captured and wrote 17.534 MB perf.data (264326 samples) ] > # cat /sys/kernel/debug/tracing/trace | tail > rs:main Q:Reg-582 [000] d..2 4858.711225: : Error: failed to > output: -95 > rs:main Q:Reg-582 [000] d..2 4858.711241: : Error: failed to > output: -95 > gmain-1858 [003] d..2 4858.711436: : Error: failed to > output: -95 > gmain-1858 [003] d..2 4858.711441: : Error: failed to > output: -95 > gmain-1858 [003] d..2 4858.711473: : Error: failed to > output: -95 > rs:main Q:Reg-582 [002] d..2 4858.712215: : Error: failed to > output: -95 > rs:main Q:Reg-582 [002] d..2 4858.712224: : Error: failed to > output: -95 > gmain-1858 [003] d..2 4858.712230: : Error: failed to > output: -95 > rs:main Q:Reg-582 [002] d..2 4858.712235: : Error: failed to > output: -95 > rs:main Q:Reg-582 [002] d..2 4858.712239: : Error: failed to > output: -95 > > System wide events can also be scheduled in and out. If the bpf-output > events > are scheduled out, trying to output data through it causes the above > failure. > I don't think it is a problem. > > Peter, Could you please give some infomation? In which case a system wide > bpf output channel would be scheduled out? >
Sorry, I think my brain is not quite well. Actually this is a easy question: all ENOTSUPP results are generated before PERF_EVENT_IOC_ENABLE or after PERF_EVENT_IOC_DISABLE. You saw so many failure messages because it is sys_write, and perf itself needs it.
So you can simply ignore these messages.
Thank you.
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