On 6/30/15 7:57 PM, He Kuang wrote:
When we add a kprobe point and record events by perf, the execution path of all threads on each cpu will enter this point, but perf may only record events on a particular thread or cpu at this kprobe point, a check on call->perf_events list filters out the threads which perf is not recording.
I think there is a better way to do that. You're adding artificial per_cpu filtering whereas you really need per_pid filtering. The patch kinda worked, but looks more by accident. The accurate way to do per_pid filtering is to automatically add 'if ((u32)bpf_get_current_pid_tgid() != expected_pid) return 0;' as the first statement of the program. You already have nice infra to add prologue to the program. So I think adding above 'if' on user space side of perf is a preferred way to achieve that. Also such per_pid filtering should be smart. The command 'perf record -a -e my_prog.o -- sleep 10' should collect all things that my_prog was attached to and not only things that happened as part of sleep. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
