This is a small blogpost on using ‘perf’. I got an error message when I tried to run ‘perf top’ systemwide:
# perf top Too many events are opened. Try again after reducing the number of events
What actually is the case here, is actually described in the perf wiki:
Open file limits
The design of the perf_event kernel interface which is used by the perf tool, is such that it uses one file descriptor per event per-thread or per-cpu.
On a 16-way system, when you do:
perf stat -e cycles sleep 1
You are effectively creating 16 events, and thus consuming 16 file descriptors.
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