add a benchmark file for IO

_oasis

@@ -191,6 +191,14 @@ Executable run_bench_hash
   MainIs: run_bench_hash.ml
   BuildDepends: containers, containers.misc
 
+Executable run_bench_io
+  Path: benchs/
+  Install: false
+  CompiledObject: best
+  Build$: flag(bench) && flag(unix) && flag(lwt)
+  MainIs: run_bench_io.ml
+  BuildDepends: containers, unix, lwt.unix, benchmark
+
 Executable run_test_future
   Path:         tests/threads/
   Install:      false

benchs/run_bench_io.ml

@@ -0,0 +1,88 @@
+
+let read_input_char file =
+  CCIO.with_in file
+    (fun ic ->
+      let count = ref 0 in
+      try
+        while true do
+          let _ = input_char ic in
+          incr count
+        done;
+        assert false
+      with End_of_file -> !count
+    )
+
+let read_input file =
+  CCIO.with_in file
+    (fun ic ->
+      let count = ref 0 in
+      let n = 4096 in
+      let b = Bytes.make n ' ' in
+      try
+        while true do
+          let n' = input ic b 0 n in
+          if n'=0 then raise Exit;
+          count := !count + n'
+        done;
+        assert false
+      with Exit ->
+        !count
+    )
+
+let read_read file =
+  let fd = Unix.openfile file [Unix.O_RDONLY] 0o644 in
+  let count = ref 0 in
+  let n = 4096 in
+  let b = Bytes.make n ' ' in
+  try
+    while true do
+      let n' = Unix.read fd b 0 n in
+      if n'=0 then raise Exit;
+      count := !count + n'
+    done;
+    assert false
+  with Exit ->
+    Unix.close fd;
+    !count
+
+let read_lwt file =
+  let open Lwt.Infix in
+  Lwt_io.with_file ~mode:Lwt_io.input file
+    (fun ic ->
+      let n = 4096 in
+      let b = Bytes.make n ' ' in
+      let rec read_chunk count =
+        Lwt_io.read_into ic b 0 n >>= fun n' ->
+        let count = count + n' in
+        if n'>0 then read_chunk count else Lwt.return count
+      in
+      read_chunk 0
+    )
+
+let read_lwt' file = Lwt_main.run (read_lwt file)
+ 
+let profile ~f file () = (f file)
+
+let bench file =
+  let n1 = read_input_char file in
+  let n2 = read_input file in
+  let n3 = read_read file in
+  let n4 = read_lwt' file in
+  Printf.printf "results: %d, %d, %d, %d\n" n1 n2 n3 n4;
+  assert (n1=n2 && n2 = n3 && n3=n4);
+  Benchmark.throughputN ~repeat:5 4
+    [ "input_char", profile ~f:read_input_char file, ()
+    ; "input", profile ~f:read_input file, ()
+    ; "Unix.read", profile ~f:read_read file, ()
+    ; "Lwt_io.read", profile ~f:read_lwt' file, ()
+    ]
+
+let () =
+  if Array.length Sys.argv < 2 then invalid_arg "use: truc file";
+  let file = Sys.argv.(1) in
+  Printf.printf "read file %s\n" file;
+  let res = bench file in
+  Benchmark.tabulate res;
+  ()
+
+