Messages in this thread | | | Date | Tue, 07 Jul 2015 18:31:07 -0700 | From | Alexei Starovoitov <> | Subject | Re: [RFC PATCH v3 0/2] Make eBPF programs output data to perf event |
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On 7/7/15 4:43 AM, He Kuang wrote: > Hi, > > The two previous versions tried to combine bpf output data with the > sample event of the attached kprobe point, which leads to problems > about perf_trace_buf. > > After discussion we found it's not necessary to combine those two > parts of information, even we do not need the orignial kprobe output > event at all. Based on this idea, the implementation becomes simple, > just like what perf do with ftrace:functions, we set up a bpf ftrace > entry for perf tools to poll and collect data on it, eBpf program use > a helper function to submit data to ring-buffer, that's all. This > implementation also leaves all issues such as sample-types to perf > commandline. > > Currently, we just use raw data in the format fields to not interfere > perf sample parser, because the raw-data can be parsed by perf script > plugin easily.
Looks much better! In general I think splitting it into two patches is confusing, since 1st patch is meaningless without 2nd. I would squash it. Other comments inline.
> bpf_output_sample(&del_time, sizeof(del_time));
typo? You meant bpf_output_data(&del_time, sizeof(del_time), ctx) ?
To match the rest of helpers, please make ctx to be first argument. Also I think bpf_output_trace_data() name is better. bpf_output_data name doesn't indicate that it's tracing only helper and might be confusing with networking helpers.
> Record bpf events: > > $ perf record -e ftrace:bpf -e sample.o -- dd if=/dev/zero of=test bs=4k count=3 > > The results showed in perf-script: > > $ perf script > dd 994 [000] 166.686779: ftrace:bpf: 8: (000000000542b426, ...) > dd 994 [000] 166.686779: ftrace:bpf: 8: (00000000001011ef, ...) > dd 994 [000] 166.686779: ftrace:bpf: 8: (000000000007a2b6, ...)
nice!
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