On 10/16/18 11:43 PM, Song Liu wrote: > I agree that processing events while recording has significant overhead. > In this case, perf user space need to know details about the the jited BPF > program. It is impossible to pass all these details to user space through > the relatively stable ring_buffer API. Therefore, some processing of the > data is necessary (get bpf prog_id from ring buffer, and then fetch program > details via BPF_OBJ_GET_INFO_BY_FD. > > I have some idea on processing important data with relatively low overhead. > Let me try implement it. >
As I understand it, you want this series: kernel: add event to perf buffer on bpf prog load userspace: perf reads the event and grabs information about the program from the fd Is that correct? Userpsace is not awakened immediately when an event is added the the ring. It is awakened once the number of events crosses a watermark. That means there is an unknown - and potentially long - time window where the program can be unloaded before perf reads the event. So no matter what you do expecting perf record to be able to process the event quickly is an unreasonable expectation.
