CP-52911: benchmark Timeslice.Runtime functions

Adds a benchmarking test for functions used in `Timeslice.Runtime`
module. This functions are meant to have low overhead and should have a
minimum of memory allocations.

Signed-off-by: Gabriel Buica <danutgabriel.buica@cloud.com>

Author: GabrielBuica

ocaml/tests/bench/bench_timeslice.ml

@@ -0,0 +1,70 @@
+open Bechamel
+
+let test_maybe_thread_yield () =
+  Sys.opaque_identity
+    (Xapi_timeslice.Timeslice.Runtime.maybe_thread_yield
+       ~global_slice_period:10_000_000
+    )
+
+let test_sched_global_slice () =
+  Sys.opaque_identity
+    (Xapi_timeslice.Timeslice.Runtime.sched_global_slice
+       ~global_slice_period:10_000_000
+    )
+
+let test_tgroups_on ~name f =
+  let allocate () =
+    let () = Atomic.set Tgroup.Cgroup.cgroup_dir (Some "") in
+    let g_cli = Some "cli" |> Tgroup.of_req_originator |> Option.get in
+    let () = Tgroup.add g_cli in
+    let tg_cli = Tgroup.group_of_description g_cli |> Option.get in
+    let _ = Atomic.fetch_and_add tg_cli.thread_count 10 in
+    let () = Tgroup.add Tgroup.Description.authenticated_root in
+    let tg_authenticated_root =
+      Tgroup.group_of_description Tgroup.Description.authenticated_root
+      |> Option.get
+    in
+    let _ = Atomic.fetch_and_add tg_authenticated_root.thread_count 5 in
+    ()
+  in
+  let free = Tgroup.destroy in
+  Test.make_with_resource ~name ~allocate ~free Test.uniq f
+
+let test_with_thread_classified ~name f =
+  let allocate () =
+    let () = Atomic.set Tgroup.Cgroup.cgroup_dir (Some "") in
+    let g_cli = Some "cli" |> Tgroup.of_req_originator |> Option.get in
+    let () = Tgroup.add g_cli in
+    let tg_cli = Tgroup.group_of_description g_cli |> Option.get in
+    let _ = Atomic.fetch_and_add tg_cli.thread_count 10 in
+    let () = Tgroup.add Tgroup.Description.authenticated_root in
+    let tg_authenticated_root =
+      Tgroup.group_of_description Tgroup.Description.authenticated_root
+      |> Option.get
+    in
+    let () = Atomic.incr tg_authenticated_root.thread_count in
+    Xapi_stdext_threads.Threadext.ThreadRuntimeContext.(
+      let thread_ctx = get () in
+      update
+        (fun thread_ctx ->
+          {thread_ctx with tgroup= Tgroup.Description.authenticated_root}
+        )
+        thread_ctx
+    )
+  in
+  let free () =
+    Tgroup.destroy () ;
+    Xapi_stdext_threads.Threadext.ThreadRuntimeContext.remove ()
+  in
+  Test.make_with_resource ~name ~allocate ~free Test.uniq f
+
+let benchmarks =
+  Test.make_grouped ~name:"timeslice"
+    [
+      test_with_thread_classified ~name:"maybe_thread_yield"
+        (Staged.stage test_maybe_thread_yield)
+    ; test_tgroups_on ~name:"sched_global_slice"
+        (Staged.stage test_sched_global_slice)
+    ]
+
+let () = Bechamel_simple_cli.cli benchmarks

ocaml/tests/bench/dune

@@ -1,5 +1,6 @@
 (executables
  (names
+  bench_timeslice
   bench_tracing
   bench_uuid
   bench_throttle2
@@ -10,6 +11,7 @@
   bechamel
   bechamel-notty
   notty.unix
+  tgroup
   tracing_export
   threads.posix
   fmt
@@ -18,4 +20,6 @@
   xapi_aux
   tests_common
   log
-  xapi_internal))
+  xapi_internal
+  xapi_timeslice
+  xapi-stdext-threads))