On Fri, 17 Jan 2025 13:04:07 +0100 Tomas Glozar <tglo...@redhat.com> wrote:
> I was thinking of turning timerlat_hist_handler/timerlat_top_handler > into a BPF program and having it executed right after the sample is > created, e.g. by using the BPF perf interface to hook it to a > tracepoint event. The histogram/counter would be stored in BPF maps, > which would be merely copied over in the main loop. This is > essentially how cyclictest does it, except in userspace. I expect this > solution to have good performance, but the obvious downside is that it > requires BPF. This is not a problem for us, but might be for other > rtla users and we'd likely have to keep both implementations of sample > processing in the code. > > Also, before even starting with that, it would be likely necessary to > remove the duplicate code throughout timerlat/osnoise and test it > properly, so we don't have to do the same code changes twice or four > times. We could also add kernel helpers to the code if it would help. Hmm, the timerlat event could probably get access to a trigger to allow it to do the work in the kernel like what the 'hist' triggers do. We can extend on that. The reason I haven't written a BPF program yet, is because when I feel there's a useful operation that can be done, I just extend ftrace to do it ;-) -- Steve
