basic test for usdt

bench/dune

@@ -21,3 +21,10 @@
  (name bench_fuchsia_write)
  (modules bench_fuchsia_write)
  (libraries benchmark trace-fuchsia))
+
+(executable
+ (name trace_usdt)
+ (modules trace_usdt)
+ (preprocess
+  (pps ppx_trace))
+ (libraries trace.core trace-usdt))

bench/trace_usdt.ml

@@ -0,0 +1,64 @@
+module Trace = Trace_core
+
+let ( let@ ) = ( @@ )
+let sleep_s = ref 0.
+
+let work ~dom_idx ~n () : unit =
+  Trace_core.set_thread_name (Printf.sprintf "worker%d" dom_idx);
+  for _i = 1 to n do
+    let%trace _sp = "outer" in
+    Trace_core.add_data_to_span _sp [ "i", `Int _i ];
+    for _k = 1 to 10 do
+      let%trace _sp = "inner" in
+
+      if !sleep_s > 0. then Thread.delay !sleep_s;
+      ()
+    done;
+
+    (* Thread.delay 1e-6 *)
+    if dom_idx = 0 && _i mod 4096 = 0 then (
+      Trace_core.message "gc stats";
+      let stat = Gc.quick_stat () in
+      Trace_core.counter_float "gc.minor" (8. *. stat.minor_words);
+      Trace_core.counter_float "gc.major" (8. *. stat.major_words)
+    )
+  done
+
+let main ~n ~j () : unit =
+  let domains =
+    Array.init j (fun dom_idx -> Domain.spawn (fun () -> work ~dom_idx ~n ()))
+  in
+
+  let%trace () = "join" in
+  Array.iter Domain.join domains
+
+let help =
+  {|bench1
+
+example use:
+```
+$ ./bench_usdt --sleep=2 &
+$ bpftrace -e 'usdt:*:probe__json /str(arg0) == "otrace:exit"/ { printf("[%d] %s %s\n", tid, str(arg0), str(arg1)) }'
+```
+|}
+
+let () =
+  let@ () = Trace_usdt.with_setup () in
+  Trace_core.set_process_name "trace_usdt1";
+  Trace_core.set_thread_name "main";
+
+  let%trace () = "main" in
+
+  let n = ref 10_000 in
+  let j = ref 4 in
+
+  let args =
+    [
+      "-n", Arg.Set_int n, " number of iterations";
+      "-j", Arg.Set_int j, " set number of workers";
+      "--sleep", Arg.Set_float sleep_s, " sleep in seconds";
+    ]
+    |> Arg.align
+  in
+  Arg.parse args ignore help;
+  main ~n:!n ~j:!j ()