Add runtime control for `profiling.sampling`

[maurycy]

Feature or enhancement

Proposal:

The idea is to add an optional control channel (socket? named pipe?), so another process can start, stop etc. profiling without killing/restarting the profiler completely. Right now, the only option is to interact with it via TUI mode or just stop it via Ctrl-C.

While working on psf/pyperf#230 I ran into the following problem: some parts (eg: warming up) of benchmarking should not be profiled, as they do not add any value. My only option was sending SIGINT signal.

Generally, the current flow is nice for headful sessions but it could be improved for (especially long-running) headless sessions.

perf record --control does it in a similar way:

       --control=fifo:ctl-fifo[,ack-fifo], --control=fd:ctl-fd[,ack-fd]
           ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as
           follows. Listen on ctl-fd descriptor for command to control
           measurement.

       Available commands:

       •   enable : enable events
       •   disable : disable events
       •   enable name : enable event name
       •   disable name : disable event name
       •   snapshot : AUX area tracing snapshot).
       •   stop : stop perf record
       •   ping : ping
       •   'evlist [-v|-g|-F] : display all events
               -F  Show just the sample frequency used for each event.
               -v  Show all fields.
               -g  Show event group information.

Specifically:

• We could start with just enable and disable initially. snapshot next but it'd be lovely to dump without loosing accumulated data. Or maybe even set_rate.
• Possible transport layers could be Unix sockets (works great on Linux) or named pipe. One option might be portable, another not?
• Possble new arguments like --control unix:/tmp/tachyon-ctl.sock or --control fifo:/tmp/tachyon-ctl, similar to what perf record --control does.

It could be also ommited from the documentation initially, so we don't limit ourselves too early.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response