Hi,
I am trying to configure 8 events in a machine which supports only 4 (so, using
multiplexing). I tried different approaches:
1) Configure 8 events independently (works as expected)
2) Configure 2 event-sets of 4 events each in counting mode (works as
expected)
3) Configure 2 event-sets of 4 events each in sampling mode (not
working right)
In case 3) I also tried different approaches:
3.a) 1 ring-buffer for each event-set and a callback for the POLL signal
- only the first ring-buffer was detecting samples
- the second ring-buffer was empty
3.b) 1 ring-buffer shared between event-sets (using
PERF_EVENT_IOC_SET_OUTPUT)
- both event-sets were writing to the ring-buffer
- 1st event-set only writes 2 samples while 2nd event-set
writes like 20+ samples
- samples from 1st event-set report time_enabled=time_running
while samples from 2nd don’t
Moreover, in both cases the wakeup_events parameter is not working.
I believe there must be some programming bugs in perf_event while profiling in
sampling mode with multiple event-sets (groups).
Regards,
matallui
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