(* Example: pipeline between processes
Here a Netmcore_buffer is used as a pipe buffer. A producer
pumps data into the pipeline, and the consumer reads it.
A Netmcore_buffer can grow to arbitrary sizes. In order to
prevent this, we put a few synchronization variables into
the header of the buffer.
*)
open Printf
type header =
{ mutable length : int;
mutable eof : bool;
mutable lock : Netmcore_mutex.mutex;
mutable have_space : Netmcore_condition.condition;
mutable have_data : Netmcore_condition.condition;
mutable wait_set : Netmcore_condition.wait_set
}
type buffer = header Netmcore_buffer.buffer
type buffer_descr = header Netmcore_buffer.buffer_descr
let pool_size = 1024 * 1024 (* 1 M *)
(* Size of the shm block *)
let max_buffer = 65536 (* 64 K *)
(* Size of the pipe buffer *)
let buf_increment = 16384
(* Pipe buffer space is allocated in units of this *)
let send_size = 16 * 1024 * 1024 * 1024 (* 16 G *)
(* This much data is sent over the pipe in total *)
let variant = `Nocopy
(* see consumer *)
(* Define the pool. This is allowed to do in the master process.
Note that the process calling create_mempool generally cannot use
the pool!
*)
let pool = Netmcore_mempool.create_mempool pool_size
let producer (bd:buffer_descr) =
(* We send (almost) endlessly the string 0123456789... *)
let b = Netmcore_buffer.buffer_of_descr pool bd in
let p_len = max_buffer - (max_buffer mod 10) + 10 in
let p = String.make p_len ' ' in
for k = 0 to p_len-1 do
p.[k] <- Char.chr(48 + (k mod 10))
done;
let h = Netmcore_buffer.header b in
let w =
(* Get a wait entry for the condition variables *)
Netmcore_heap.modify
(Netmcore_buffer.heap b)
(fun mut ->
Netmcore_condition.alloc_wait_entry mut h.wait_set
) in
let n = ref 0 in
let q = ref 0 in
while !n < send_size do
let l = (
let l_ref = ref 0 in
Netmcore_mutex.lock h.lock;
while h.length >= max_buffer do
Netmcore_condition.wait w h.have_space h.lock
done;
l_ref := h.length;
Netmcore_mutex.unlock h.lock;
!l_ref
) in
let space = max_buffer - l in
let to_send0 = min (send_size - !n) space in
let to_send = ref to_send0 in
(* printf "after %d bytes, sending %d bytes\n%!" !n to_send0; *)
while !to_send > 0 do
let m = min !to_send (p_len - !q) in
Netmcore_buffer.add_sub_string b p !q m;
to_send := !to_send - m;
q := (!q + m) mod 10;
n := !n + m;
done;
Netmcore_mutex.lock h.lock;
h.length <- h.length + to_send0;
h.eof <- !n = send_size;
Netmcore_mutex.unlock h.lock;
Netmcore_condition.signal h.have_data
done
let producer_fork, producer_join =
Netmcore_process.def_process producer
let one_meg = float (1024 * 1024)
let consumer (bd:buffer_descr) =
(* We compute a checksum, just to do something with the data *)
let b = Netmcore_buffer.buffer_of_descr pool bd in
let cksum = ref 0 in
let t0 = Unix.gettimeofday() in
let t1 = ref t0 in
let n1 = ref 0 in
let h = Netmcore_buffer.header b in
let w =
Netmcore_heap.modify
(Netmcore_buffer.heap b)
(fun mut ->
Netmcore_condition.alloc_wait_entry mut h.wait_set
) in
let continue = ref true in
let i = ref 0 in
while !continue do
let l = (
let l_ref = ref 0 in
Netmcore_mutex.lock h.lock;
while h.length = 0 do
Netmcore_condition.wait w h.have_data h.lock
done;
l_ref := h.length;
continue := not h.eof;
Netmcore_mutex.unlock h.lock;
!l_ref
) in
(* We implement here two variants:
(1) Copy data immediately, signal, then evaluate data
(good if evaluation is expensive)
(2) Evaluate data on the original string, then signal
(good if evaluation is cheap)
*)
let process s pos len =
for k = 0 to len-1 do
let c = Char.code (String.unsafe_get s (pos+k)) in
cksum := (!cksum lsl 3) + c
done;
i := !i + len;
n1 := !n1 + len in
let postprocess () =
let t = Unix.gettimeofday() in
if t -. !t1 >= 1.0 then (
printf "received %d bytes, %.1f M/s\n%!"
!n1 ((float !n1 /. (t -. !t1)) /. one_meg);
n1 := 0;
t1 := t;
) in
let signal len =
Netmcore_mutex.lock h.lock;
h.length <- h.length - len;
Netmcore_mutex.unlock h.lock;
Netmcore_condition.signal h.have_space in
match variant with
| `Copy ->
let s = Netmcore_buffer.sub b !i l in
Netmcore_buffer.delete_hd b l;
signal l;
process s 0 l;
postprocess()
| `Nocopy ->
let r = ref 0 in
while !r < l do
Netmcore_buffer.access b !i
(fun s pos len ->
let len' = min len (l - !r) in
process s pos len';
r := !r + len';
)
done;
Netmcore_buffer.delete_hd b l;
signal l;
postprocess()
done;
let t = Unix.gettimeofday() in
printf "Total: received %d bytes, %.1f M/s\n%!"
!i ((float !i /. (t -. t0)) /. one_meg);
printf "Checksum: %d\n%!" (!cksum land 0x3fff_ffff)
let consumer_fork, consumer_join =
Netmcore_process.def_process consumer
let control() =
(* Create the buffer. Note that synchronization variables must be
directly created in shared memory. To do so, we first use
dummy values (h_orig is in normal memory), and after the header
has been copied to shm, we do the real initialization.
*)
let h_orig =
{ length = 0;
eof = false;
lock = Netmcore_mutex.dummy();
have_space = Netmcore_condition.dummy_condition();
have_data = Netmcore_condition.dummy_condition();
wait_set = Netmcore_condition.dummy_wait_set()
} in
let b = Netmcore_buffer.create pool buf_increment h_orig in
Netmcore_heap.modify
(Netmcore_buffer.heap b)
(fun mut ->
(* N.B. h is a copy of h_orig residing in shm *)
let h = Netmcore_buffer.header b in
h.lock <- Netmcore_mutex.create mut `Normal;
h.have_space <- Netmcore_condition.create_condition mut;
h.have_data <- Netmcore_condition.create_condition mut;
h.wait_set <- Netmcore_condition.create_wait_set mut;
);
(* Now start the workers for producing and consuming data *)
let producer_pid =
Netmcore_process.start
~inherit_resources:`All
producer_fork (Netmcore_buffer.descr_of_buffer b) in
let consumer_pid =
Netmcore_process.start
~inherit_resources:`All
consumer_fork (Netmcore_buffer.descr_of_buffer b) in
(* Now wait until these processes are done *)
( match Netmcore_process.join producer_join producer_pid with
| None ->
failwith "Error in the producer"
| Some _ ->
()
);
( match Netmcore_process.join consumer_join consumer_pid with
| None ->
failwith "Error in the consumer"
| Some _ ->
()
);
(* Cleanup: *)
let h = Netmcore_buffer.header b in
Netmcore_mutex.destroy h.lock;
Netmcore_condition.destroy_condition h.have_space;
Netmcore_condition.destroy_condition h.have_data;
Netmcore_condition.destroy_wait_set h.wait_set;
Netmcore_buffer.destroy b
let control_fork, control_join =
Netmcore_process.def_process control
let () =
(* Netmcore_mempool.Debug.enable_alloc := true; *)
Netmcore.startup
~socket_directory:"run_pipeline"
~first_process:(fun () ->
Netmcore_process.start
~inherit_resources:`All control_fork ())
()
