Re: [PATCH v2 net-next] bpf: fix bpf_perf_event_read() helper

From: Alexei Starovoitov
Date: Thu Oct 22 2015 - 01:01:00 EST


On 10/21/15 9:49 PM, Wangnan (F) wrote:
After applying this patch I'm unable to use perf passing perf_event
again like this:

please do not top post and trim your replies.

# perf record -a -e evt=cycles -e
./test_config_map.c/maps.pmu_map.event=evt/ --exclude-perf ls

With -v it output:

...
adding perf_bpf_probe:func_write
adding perf_bpf_probe:func_write to 0x367d6a0
add bpf event perf_bpf_probe:func_write_return and attach bpf program 6
adding perf_bpf_probe:func_write_return
adding perf_bpf_probe:func_write_return to 0x3a7fc40
mmap size 528384B
ERROR: failed to insert value to pmu_map[0]
ERROR: Apply config to BPF failed: Invalid option for map, add -v to see
detail
Opening /sys/kernel/debug/tracing//kprobe_events write=
...

Looks like perf sets attr.inherit for cycles? I'll look into this problem.

yes. that's perf default.
How did it even work before?!
I was testing with your samples/bpf/tracex6 that sets inherit to zero.

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