diff --git a/ocaml/tests/bench/bench_throttle2.ml b/ocaml/tests/bench/bench_throttle2.ml
new file mode 100644
index 00000000000..50582eff4cc
--- /dev/null
+++ b/ocaml/tests/bench/bench_throttle2.ml
@@ -0,0 +1,86 @@
+open Bechamel
+
+let () =
+  Suite_init.harness_init () ;
+  Debug.set_level Syslog.Warning
+
+let __context, _ = Test_event_common.event_setup_common ()
+
+let allocate_tasks n =
+  ( __context
+  , Array.init n @@ fun i ->
+    let label = Printf.sprintf "task %d" i in
+    Xapi_task.create ~__context ~label ~description:"test task"
+  )
+
+let free_tasks (__context, tasks) =
+  let () =
+    tasks |> Array.iter @@ fun self -> Xapi_task.destroy ~__context ~self
+  in
+  ()
+
+let set_pending tasks =
+  tasks
+  |> Array.iter @@ fun self ->
+     Xapi_task.set_status ~__context ~self ~value:`pending
+
+let run_tasks _n (__context, tasks) =
+  set_pending tasks ;
+  let () =
+    tasks
+    |> Array.iter @@ fun self ->
+       Xapi_task.set_status ~__context ~self ~value:`success
+  in
+  tasks |> Array.iter @@ fun t -> Helpers.Task.wait_for ~__context ~tasks:[t]
+
+let run_tasks' _n (__context, tasks) =
+  set_pending tasks ;
+  let () =
+    tasks
+    |> Array.iter @@ fun self ->
+       Xapi_task.set_status ~__context ~self ~value:`success
+  in
+  Helpers.Task.wait_for ~__context ~tasks:(Array.to_list tasks)
+
+module D = Debug.Make (struct let name = __MODULE__ end)
+
+let run_tasks'' n (__context, tasks) =
+  set_pending tasks ;
+  let finished = Atomic.make 0 in
+  let (t : Thread.t) =
+    Thread.create
+      (fun () ->
+        for _ = 1 to 10 do
+          Thread.yield ()
+        done ;
+        tasks
+        |> Array.iter @@ fun self ->
+           Xapi_task.set_status ~__context ~self ~value:`success ;
+           Atomic.incr finished
+      )
+      ()
+  in
+  Helpers.Task.wait_for ~__context ~tasks:(Array.to_list tasks) ;
+  let f = Atomic.get finished in
+  assert (f = n || f = n - 1) ;
+  Thread.join t
+
+let benchmarks =
+  Test.make_grouped ~name:"Task latency"
+    [
+      Test.make_indexed_with_resource ~name:"task complete+wait latency"
+        ~args:[1; 10; 100] Test.multiple ~allocate:allocate_tasks
+        ~free:free_tasks (fun n -> Staged.stage (run_tasks n)
+      )
+    ; Test.make_indexed_with_resource ~name:"task complete+wait all latency"
+        ~args:[1; 10; 100] Test.multiple ~allocate:allocate_tasks
+        ~free:free_tasks (fun n -> Staged.stage (run_tasks' n)
+      )
+    ; Test.make_indexed_with_resource
+        ~name:"task complete+wait all latency (thread)" ~args:[1; 10; 100]
+        Test.multiple ~allocate:allocate_tasks ~free:free_tasks (fun n ->
+          Staged.stage (run_tasks'' n)
+      )
+    ]
+
+let () = Bechamel_simple_cli.cli benchmarks
diff --git a/ocaml/tests/bench/dune b/ocaml/tests/bench/dune
index dcd61813e1e..10cffadb857 100644
--- a/ocaml/tests/bench/dune
+++ b/ocaml/tests/bench/dune
@@ -1,4 +1,4 @@
 (executables
-	(names bench_tracing bench_uuid)
-	(libraries tracing bechamel bechamel-notty notty.unix tracing_export threads.posix fmt notty uuid)
+	(names bench_tracing bench_uuid bench_throttle2)
+	(libraries tracing bechamel bechamel-notty notty.unix tracing_export threads.posix fmt notty uuid xapi_aux tests_common log xapi_internal)
 )
diff --git a/ocaml/xapi-cli-server/cli_operations.ml b/ocaml/xapi-cli-server/cli_operations.ml
index 1e8ba0f3b37..4f61e843140 100644
--- a/ocaml/xapi-cli-server/cli_operations.ml
+++ b/ocaml/xapi-cli-server/cli_operations.ml
@@ -2848,8 +2848,6 @@ exception Finished
 let event_wait_gen rpc session_id classname record_matches =
   (* Immediately register *)
   let classes = [classname] in
-  Client.Event.register ~rpc ~session_id ~classes ;
-  debug "Registered for events" ;
   (* Check to see if the condition is already satisfied - get all objects of whatever class specified... *)
   let poll () =
     let current_tbls =
@@ -2930,96 +2928,111 @@ let event_wait_gen rpc session_id classname record_matches =
     in
     List.exists record_matches all_recs
   in
-  finally
-    (fun () ->
-      if not (poll ()) then
-        try
-          while true do
-            try
-              let events =
-                Event_types.events_of_rpc (Client.Event.next ~rpc ~session_id)
-              in
-              let doevent event =
-                let tbl =
-                  match Event_helper.record_of_event event with
-                  | Event_helper.VM (r, Some x) ->
-                      let record = vm_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.VDI (r, Some x) ->
-                      let record = vdi_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.SR (r, Some x) ->
-                      let record = sr_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.Host (r, Some x) ->
-                      let record = host_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.Network (r, Some x) ->
-                      let record = net_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.VIF (r, Some x) ->
-                      let record = vif_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.PIF (r, Some x) ->
-                      let record = pif_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.VBD (r, Some x) ->
-                      let record = vbd_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.PBD (r, Some x) ->
-                      let record = pbd_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.Pool (r, Some x) ->
-                      let record = pool_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.Task (r, Some x) ->
-                      let record = task_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.VMSS (r, Some x) ->
-                      let record = vmss_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | Event_helper.Secret (r, Some x) ->
-                      let record = secret_record rpc session_id r in
-                      record.setrefrec (r, x) ;
-                      record.fields
-                  | _ ->
-                      failwith
-                        ("Cli listening for class '"
-                        ^ classname
-                        ^ "' not currently implemented"
-                        )
-                in
-                let record =
-                  List.map (fun r -> (r.name, fun () -> safe_get_field r)) tbl
-                in
-                if record_matches record then raise Finished
+  let use_event_next = !Constants.use_event_next in
+  let run () =
+    if not (poll ()) then
+      try
+        let token = ref "" in
+        while true do
+          let events =
+            if use_event_next then
+              Event_types.events_of_rpc (Client.Event.next ~rpc ~session_id)
+            else
+              let event_from =
+                Event_types.event_from_of_rpc
+                  (Client.Event.from ~rpc ~session_id ~timeout:30. ~token:!token
+                     ~classes
+                  )
               in
-              List.iter doevent
-                (List.filter (fun e -> e.Event_types.snapshot <> None) events)
-            with
-            | Api_errors.Server_error (code, _)
-            when code = Api_errors.events_lost
-            ->
-              debug "Got EVENTS_LOST; reregistering" ;
-              Client.Event.unregister ~rpc ~session_id ~classes ;
-              Client.Event.register ~rpc ~session_id ~classes ;
-              if poll () then raise Finished
-          done
-        with Finished -> ()
-    )
-    (fun () -> Client.Event.unregister ~rpc ~session_id ~classes)
+              token := event_from.token ;
+              event_from.events
+          in
+          let doevent event =
+            let tbl =
+              match Event_helper.record_of_event event with
+              | Event_helper.VM (r, Some x) ->
+                  let record = vm_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.VDI (r, Some x) ->
+                  let record = vdi_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.SR (r, Some x) ->
+                  let record = sr_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.Host (r, Some x) ->
+                  let record = host_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.Network (r, Some x) ->
+                  let record = net_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.VIF (r, Some x) ->
+                  let record = vif_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.PIF (r, Some x) ->
+                  let record = pif_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.VBD (r, Some x) ->
+                  let record = vbd_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.PBD (r, Some x) ->
+                  let record = pbd_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.Pool (r, Some x) ->
+                  let record = pool_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.Task (r, Some x) ->
+                  let record = task_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.VMSS (r, Some x) ->
+                  let record = vmss_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | Event_helper.Secret (r, Some x) ->
+                  let record = secret_record rpc session_id r in
+                  record.setrefrec (r, x) ;
+                  record.fields
+              | _ ->
+                  failwith
+                    ("Cli listening for class '"
+                    ^ classname
+                    ^ "' not currently implemented"
+                    )
+            in
+            let record =
+              List.map (fun r -> (r.name, fun () -> safe_get_field r)) tbl
+            in
+            if record_matches record then raise_notrace Finished
+          in
+          List.iter doevent
+            (List.filter (fun e -> e.Event_types.snapshot <> None) events)
+        done
+      with
+      | Api_errors.Server_error (code, _)
+        when code = Api_errors.events_lost && use_event_next ->
+          debug "Got EVENTS_LOST; reregistering" ;
+          Client.Event.unregister ~rpc ~session_id ~classes ;
+          Client.Event.register ~rpc ~session_id ~classes ;
+          if poll () then raise Finished
+      | Finished ->
+          ()
+  in
+  if use_event_next then (
+    Client.Event.register ~rpc ~session_id ~classes ;
+    debug "Registered for events" ;
+    finally run (fun () -> Client.Event.unregister ~rpc ~session_id ~classes)
+  ) else
+    run ()
 
 (* We're done. Unregister and finish *)
 
diff --git a/ocaml/xapi-cli-server/cli_util.ml b/ocaml/xapi-cli-server/cli_util.ml
index 48fd9392ef5..75c4f30360f 100644
--- a/ocaml/xapi-cli-server/cli_util.ml
+++ b/ocaml/xapi-cli-server/cli_util.ml
@@ -42,21 +42,41 @@ exception Cli_failure of string
 
 (** call [callback task_record] on every update to the task, until it completes or fails *)
 let track callback rpc (session_id : API.ref_session) task =
-  let classes = ["task"] in
+  let use_event_next = !Constants.use_event_next in
+  let classes =
+    if use_event_next then
+      ["task"]
+    else
+      [Printf.sprintf "task/%s" (Ref.string_of task)]
+  in
   finally
     (fun () ->
       let finished = ref false in
       while not !finished do
-        Client.Event.register ~rpc ~session_id ~classes ;
+        if use_event_next then
+          Client.Event.register ~rpc ~session_id ~classes ;
         try
           (* Need to check once after registering to avoid a race *)
           finished :=
             Client.Task.get_status ~rpc ~session_id ~self:task <> `pending ;
+          let token = ref "" in
           while not !finished do
             let events =
-              Event_types.events_of_rpc (Client.Event.next ~rpc ~session_id)
+              if use_event_next then
+                let events =
+                  Event_types.events_of_rpc (Client.Event.next ~rpc ~session_id)
+                in
+                List.map Event_helper.record_of_event events
+              else
+                let event_from =
+                  Event_types.event_from_of_rpc
+                    (Client.Event.from ~rpc ~session_id ~classes ~token:!token
+                       ~timeout:30.
+                    )
+                in
+                token := event_from.token ;
+                List.map Event_helper.record_of_event event_from.events
             in
-            let events = List.map Event_helper.record_of_event events in
             List.iter
               (function
                 | Event_helper.Task (t, Some t_rec) when t = task ->
diff --git a/ocaml/xapi-consts/constants.ml b/ocaml/xapi-consts/constants.ml
index 2c7fc49e179..d3ee0bf8531 100644
--- a/ocaml/xapi-consts/constants.ml
+++ b/ocaml/xapi-consts/constants.ml
@@ -275,6 +275,9 @@ let owner_key = "owner"
 
 (* set in VBD other-config to indicate that clients can delete the attached VDI on VM uninstall if they want.. *)
 
+(* xapi-cli-server doesn't link xapi-globs *)
+let use_event_next = ref true
+
 (* the time taken to wait before restarting in a different mode for pool eject/join operations *)
 let fuse_time = ref 10.
 
diff --git a/ocaml/xapi-types/event_types.ml b/ocaml/xapi-types/event_types.ml
index fcd8840e59f..83c82b0bc8d 100644
--- a/ocaml/xapi-types/event_types.ml
+++ b/ocaml/xapi-types/event_types.ml
@@ -77,6 +77,24 @@ let rec rpc_of_event_from e =
     ; ("token", rpc_of_token e.token)
     ]
 
+(* xmlrpc and jsonrpc would map Int32 to Int, but int32_of_rpc can't actually parse
+    an Int32 back as an int32... this is a bug in ocaml-rpc that should be fixed.
+    meanwhile work it around by mapping Rpc.Int32 to Rpc.Int upon receiving the message
+   (it is only Rpc.Int32 for backward compat with non-XAPI Xmlrpc clients)
+*)
+
+let rec fixup_int32 = function
+  | Rpc.Dict dict ->
+      Rpc.Dict (List.map fixup_kv dict)
+  | Rpc.Int32 i ->
+      Rpc.Int (Int64.of_int32 i)
+  | rpc ->
+      rpc
+
+and fixup_kv (k, v) = (k, fixup_int32 v)
+
+let event_from_of_rpc rpc = rpc |> fixup_int32 |> event_from_of_rpc
+
 (** Return result of an events.from call *)
 
 open Printf
diff --git a/ocaml/xapi/taskHelper.mli b/ocaml/xapi/taskHelper.mli
index dc5d76cf65b..1c4d5381586 100644
--- a/ocaml/xapi/taskHelper.mli
+++ b/ocaml/xapi/taskHelper.mli
@@ -36,6 +36,9 @@ val set_result : __context:Context.t -> Rpc.t option -> unit
 
 val status_is_completed : [> `cancelled | `failure | `success] -> bool
 
+val status_to_string :
+  [< `pending | `success | `failure | `cancelling | `cancelled] -> string
+
 val complete : __context:Context.t -> Rpc.t option -> unit
 
 val set_cancellable : __context:Context.t -> unit
diff --git a/ocaml/xapi/xapi_globs.ml b/ocaml/xapi/xapi_globs.ml
index efdcabfbdb6..0c061731924 100644
--- a/ocaml/xapi/xapi_globs.ml
+++ b/ocaml/xapi/xapi_globs.ml
@@ -1395,6 +1395,11 @@ let other_options =
     , (fun () -> string_of_bool !Db_globs.idempotent_map)
     , "True if the add_to_<map> API calls should be idempotent"
     )
+  ; ( "use-event-next"
+    , Arg.Set Constants.use_event_next
+    , (fun () -> string_of_bool !Constants.use_event_next)
+    , "Use deprecated Event.next instead of Event.from"
+    )
   ; ( "nvidia_multi_vgpu_enabled_driver_versions"
     , Arg.String
         (fun x ->