On Thu, Dec 22, 2022 at 09:34:42AM -0800, Namhyung Kim wrote: > Sorry about that. Let me rephrase it like below: > > With bpf_cast_to_kern_ctx(), BPF programs attached to a perf event > can access perf sample data directly from the ctx. This is the bpf_prog_run() in bpf_overflow_handler(), right? > But the perf sample > data is not fully prepared at this point, and some fields can have invalid > uninitialized values. So it needs to call perf_prepare_sample() before > calling the BPF overflow handler. It never was, why is it a problem now? > But just calling perf_prepare_sample() can be costly when the BPF So you potentially call it twice now, how's that useful?
