Employ an approach that avoids copying contents of received network p…

…ackets.
pgj · Aug 23, 2012 · fb0077a · fb0077a
1 parent ecb4a60
commit fb0077a
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Showing 5 changed files with 167 additions and 151 deletions.
diff --git a/packages/mirage-platform/lib/netif.ml b/packages/mirage-platform/lib/netif.ml
@@ -28,88 +28,19 @@
 open Lwt
 open Printf
 
-type sring = {
-    buf: Io_page.t;
-    header_size: int;
-    slot_size: int;
-    nr_ents: int;
-}
-
-let sring_hdr_size = 64 (* sizeof(struct sring_hdr) *)
-
-cstruct sring_hdr {
-    uint16_t sr_cur;
-    uint16_t sr_avail;
-    uint16_t sr_size;
-    uint16_t sr_slotsize;
-    uint8_t  sr_pad[56]
-} as little_endian
-
-let sslot_size = 2 (* sizeof(struct sslot) *)
-
-cstruct sslot {
-    uint16_t ss_len
-} as little_endian
-
-let nr_ents sring = sring.nr_ents
-
-let avail_packet sring =
-  let hdr = Io_page.sub sring.buf 0 sring.header_size in
-  get_sring_hdr_sr_avail hdr
-
-let slot sring i =
-  let idx = i land (sring.nr_ents - 1) in
-  let off = sring.header_size + (idx * sslot_size) in
-  let s = Io_page.sub sring.buf off sslot_size in
-  let size = get_sslot_ss_len s in
-  let off = sring.header_size + (sring.nr_ents * sslot_size) +
-    (idx * sring.slot_size) in
-  Io_page.sub sring.buf off size
-
-let top_packet sring = slot sring (get_sring_hdr_sr_cur (sring.buf))
-
-let pop_packet sring =
-  let b = sring.buf in
-  let i = get_sring_hdr_sr_cur b in
-  let n = get_sring_hdr_sr_avail b in
-  set_sring_hdr_sr_cur b ((i + 1) land (sring.nr_ents - 1));
-  set_sring_hdr_sr_avail b (n - 1);
-  return ()
-
-let of_buf buf slot_size =
-  let power_of_2 x =
-    let x = x lor (x lsr 1) in
-    let x = x lor (x lsr 2) in
-    let x = x lor (x lsr 4) in
-    let x = x lor (x lsr 8) in
-    let x = x lor (x lsr 16) in
-    let x = x lor (x lsr 32) in
-    x - (x lsr 1)
-  in
-  let header_size = sring_hdr_size in
-  let total = Io_page.length buf in
-  let free_bytes = total - header_size in
-  let nr_ents = power_of_2 (free_bytes / slot_size) in
-  assert (header_size + (nr_ents * (sslot_size + slot_size)) < total);
-  set_sring_hdr_sr_cur buf 0;
-  set_sring_hdr_sr_avail buf 0;
-  set_sring_hdr_sr_size buf nr_ents;
-  set_sring_hdr_sr_slotsize buf slot_size;
-  { buf; header_size; slot_size; nr_ents }
-
 type t = {
     backend_id: int;
     backend: string;
     mac: string;
     mutable active: bool;
-    rx_ring: sring;
 }
 
 type id = string
 
 external get_vifs: unit -> id list = "caml_get_vifs"
-external plug_vif: id -> Io_page.t -> bool * int * string = "caml_plug_vif"
+external plug_vif: id -> bool * int * string = "caml_plug_vif"
 external unplug_vif: id -> unit = "caml_unplug_vif"
+external get_mbufs : int -> Io_page.t list = "caml_get_mbufs"
 
 let devices : (id, t) Hashtbl.t = Hashtbl.create 1
 
@@ -128,10 +59,8 @@ let plug id =
     return (Hashtbl.find devices id)
   with Not_found ->
     let backend = id in
-    let buf = Io_page.get ~pages_per_block:33 () in
+    let active,backend_id,mac = plug_vif id in
-    let rx_ring = of_buf buf 2048 in
+    let t = { backend_id; backend; mac; active } in
-    let active,backend_id,mac = plug_vif id buf in
-    let t = { backend_id; backend; mac; active; rx_ring } in
     Hashtbl.add devices id t;
     return t
 
@@ -161,10 +90,12 @@ let writev ifc pages =
   return ()
 
 let rx_poll ifc fn =
-  while_lwt (avail_packet ifc.rx_ring > 0) do
+  let mbufs = get_mbufs ifc.backend_id in
-    fn (top_packet ifc.rx_ring) >>
+  Lwt_list.iter_s (fun m ->
-    pop_packet ifc.rx_ring
+    try_lwt fn m
-  done
+    with exn ->
+      return (printf "Exception on receive: %s\n%!" (Printexc.to_string exn)))
+  mbufs
 
 let listen ifc fn =
   let rec poll_t () =