On Tue, Jan 09, 2024 at 08:20:57AM -0500, Steven Rostedt wrote: > > Hi Masami, thanks for looking at this. > > On Tue, 9 Jan 2024 22:04:45 +0900 > Masami Hiramatsu (Google) <[email protected]> wrote: > > > > The tracing ring-buffers can be stored on disk or sent to network > > > without any copy via splice. However the later doesn't allow real time > > > processing of the traces. A solution is to give userspace direct access > > > to the ring-buffer pages via a mapping. An application can now become a > > > consumer of the ring-buffer, in a similar fashion to what trace_pipe > > > offers. > > > > I think this is very nice feature. But this series seems just a feature, > > no document and no example code. Can you add 2 patches to add those? > > I know libtracefs already provide a support code, but I think it is > > better to have a test code under tools/testing/selftests/ring_buffer. > > Yeah, we should have sample code and a test.
Ack. I will recycle what I had in the cover letter in a ring_buffer selftest. > > > > > I also wonder what happen if other operation (e.g. taking snapshot) happens > > while mmaping the ring buffer. > > Hmm, good point. We should disable snapshots when mapped, and also prevent > mapping with latency tracer if we are not already doing that. ring_buffer_swap_cpu() is already disabled when mapped as well as resize_disabled set. Is something else necessary? > > -- Steve
