Re: [RFC PATCH 0/4] perf tools: Use the new ability of eBPF programs to access hardware PMU counter

From: Alexei Starovoitov
Date: Fri Aug 28 2015 - 21:28:40 EST

On 8/27/15 3:42 AM, Kaixu Xia wrote:
An example is pasted at the bottom of this cover letter. In that example,
we can get the cpu_cycles and exception taken in sys_write.

$ cat /sys/kernel/debug/tracing/trace_pipe
$ ./perf record --event perf-bpf.o ls
cat-1653 [003] d..1 88174.613854: : ente: CPU-3 cyc:48746333 exc:84
cat-1653 [003] d..2 88174.613861: : exit: CPU-3 cyc:48756041 exc:84

nice. probably more complex example that computes the delta of the pmu
counters on the kernel side would be even more interesting.
Do you think you can extend 'perf stat' with a flag that does
stats collection for a given kernel or user function instead of the
whole process ?
Then we can use perf record/report to figure out hot functions and
follow with 'perf stat -f my_hot_func my_process' to drill into
particular function stats.

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