[processpool] schedule work to idle workers once per refresh cycle

Reviewed By: mbouaziz

Differential Revision: D15373840

fbshipit-source-id: 77359a243

infer/src/base/ProcessPool.ml

@@ -162,24 +162,21 @@ let process_updates pool buffer =
   has_dead_child pool
   |> Option.iter ~f:(fun (slot, status) ->
          killall pool ~slot (Unix.Exit_or_signal.to_string_hum status) ) ;
-  match wait_for_updates pool buffer with
-  | Some (UpdateStatus (slot, t, status)) ->
+  (* try to schedule more work if there is an idle worker *)
+  Array.findi pool.pending_items ~f:(fun _idx item -> Option.is_none item)
+  |> Option.iter ~f:(fun (idle_slot, _) -> send_work_to_child pool idle_slot) ;
+  wait_for_updates pool buffer
+  |> Option.iter ~f:(function
+       | UpdateStatus (slot, t, status) ->
            TaskBar.update_status pool.task_bar ~slot t status
-  | Some (Crash slot) ->
+       | Crash slot ->
            let {pid} = pool.slots.(slot) in
            (* clean crash, give the child process a chance to cleanup *)
            Unix.wait (`Pid pid) |> ignore ;
            killall pool ~slot "see backtrace above"
-  | Some (Ready slot) ->
+       | Ready slot ->
            TaskBar.tasks_done_add pool.task_bar 1 ;
-      send_work_to_child pool slot
-  | None -> (
-    (* no updates, so try to schedule more work if there is an idle worker *)
-    match Array.findi pool.pending_items ~f:(fun _idx item -> Option.is_none item) with
-    | None ->
-        ()
-    | Some (idle_slot, _) ->
-        send_work_to_child pool idle_slot )
+           send_work_to_child pool slot )
 
 
 (** terminate all worker processes *)