sock: Add sock_impl option to disable zero copy on send

Zero copy send can cause performance degradation with small
payloads. This patch adds an option to disable it if required. By
default zero copy is enabled.

Signed-off-by: Evgeniy Kochetov <evgeniik@mellanox.com>
Change-Id: I14f2b21ad375e770cb08f850360898bac675b351
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/3344
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Community-CI: Mellanox Build Bot
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>

CHANGELOG.md

@@ -110,6 +110,9 @@ based socket tests for iSCSI target and also the tests for SPDK NVMe-oF tcp tran
 Added `enable_recv_pipe` socket layer option to allow disabling of double buffering on receive.
 New option is used only in posix implementation.
 
+Added `enable_zerocopy_send` socket layer option to allow disabling of zero copy flow on send.
+New option is used only in posix implementation.
+
 ### vhost
 
 The function `spdk_vhost_blk_get_dev` has been removed.

doc/jsonrpc.md

@@ -6587,6 +6587,7 @@ Example response:
     "recv_buf_size": 2097152,
     "send_buf_size": 2097152,
     "enable_recv_pipe": true
+    "enable_zerocopy_send": true
   }
 }
 ~~~
@@ -6603,6 +6604,7 @@ impl_name               | Required | string      | Name of socket implementation
 recv_buf_size           | Optional | number      | Size of socket receive buffer in bytes
 send_buf_size           | Optional | number      | Size of socket send buffer in bytes
 enable_recv_pipe        | Optional | boolean     | Enable or disable receive pipe
+enable_zerocopy_send    | Optional | boolean     | Enable or disable zero copy on send
 
 ### Response
 
@@ -6622,6 +6624,7 @@ Example request:
     "recv_buf_size": 2097152,
     "send_buf_size": 2097152,
     "enable_recv_pipe": false
+    "enable_zerocopy_send": true
   }
 }
 ~~~

include/spdk/sock.h

@@ -102,6 +102,11 @@ struct spdk_sock_impl_opts {
 	 * Enable or disable receive pipe. Used by posix socket module.
 	 */
 	bool enable_recv_pipe;
+
+	/**
+	 * Enable or disable use of zero copy flow on send. Used by posix socket module.
+	 */
+	bool enable_zerocopy_send;
 };
 
 /**

lib/sock/sock.c

@@ -776,6 +776,7 @@ spdk_sock_write_config_json(struct spdk_json_write_ctx *w)
 			spdk_json_write_named_uint32(w, "recv_buf_size", opts.recv_buf_size);
 			spdk_json_write_named_uint32(w, "send_buf_size", opts.send_buf_size);
 			spdk_json_write_named_bool(w, "enable_recv_pipe", opts.enable_recv_pipe);
+			spdk_json_write_named_bool(w, "enable_zerocopy_send", opts.enable_zerocopy_send);
 			spdk_json_write_object_end(w);
 			spdk_json_write_object_end(w);
 		} else {

lib/sock/sock_rpc.c

@@ -74,6 +74,7 @@ rpc_sock_impl_get_options(struct spdk_jsonrpc_request *request,
 	spdk_json_write_named_uint32(w, "recv_buf_size", sock_opts.recv_buf_size);
 	spdk_json_write_named_uint32(w, "send_buf_size", sock_opts.send_buf_size);
 	spdk_json_write_named_bool(w, "enable_recv_pipe", sock_opts.enable_recv_pipe);
+	spdk_json_write_named_bool(w, "enable_zerocopy_send", sock_opts.enable_zerocopy_send);
 	spdk_json_write_object_end(w);
 	spdk_jsonrpc_end_result(request, w);
 	free(impl_name);
@@ -103,6 +104,10 @@ static const struct spdk_json_object_decoder rpc_sock_impl_set_opts_decoders[] =
 		"enable_recv_pipe", offsetof(struct spdk_rpc_sock_impl_set_opts, sock_opts.enable_recv_pipe),
 		spdk_json_decode_bool, true
 	},
+	{
+		"enable_zerocopy_send", offsetof(struct spdk_rpc_sock_impl_set_opts, sock_opts.enable_zerocopy_send),
+		spdk_json_decode_bool, true
+	},
 };
 
 static void

module/sock/posix/posix.c

@@ -82,7 +82,8 @@ struct spdk_posix_sock_group_impl {
 static struct spdk_sock_impl_opts g_spdk_posix_sock_impl_opts = {
 	.recv_buf_size = MIN_SO_RCVBUF_SIZE,
 	.send_buf_size = MIN_SO_SNDBUF_SIZE,
-	.enable_recv_pipe = true
+	.enable_recv_pipe = true,
+	.enable_zerocopy_send = true
 };
 
 static int
@@ -326,7 +327,7 @@ posix_sock_alloc(int fd, bool enable_zero_copy)
 	sock->fd = fd;
 
 #ifdef SPDK_ZEROCOPY
-	if (!enable_zero_copy) {
+	if (!enable_zero_copy || !g_spdk_posix_sock_impl_opts.enable_zerocopy_send) {
 		return sock;
 	}
 
@@ -1336,6 +1337,7 @@ posix_sock_impl_get_opts(struct spdk_sock_impl_opts *opts, size_t *len)
 	GET_FIELD(recv_buf_size);
 	GET_FIELD(send_buf_size);
 	GET_FIELD(enable_recv_pipe);
+	GET_FIELD(enable_zerocopy_send);
 
 #undef GET_FIELD
 #undef FIELD_OK
@@ -1363,6 +1365,7 @@ posix_sock_impl_set_opts(const struct spdk_sock_impl_opts *opts, size_t len)
 	SET_FIELD(recv_buf_size);
 	SET_FIELD(send_buf_size);
 	SET_FIELD(enable_recv_pipe);
+	SET_FIELD(enable_zerocopy_send);
 
 #undef SET_FIELD
 #undef FIELD_OK

scripts/rpc.py

@@ -2398,7 +2398,8 @@ Format: 'user:u1 secret:s1 muser:mu1 msecret:ms1,user:u2 secret:s2 muser:mu2 mse
                                        impl_name=args.impl,
                                        recv_buf_size=args.recv_buf_size,
                                        send_buf_size=args.send_buf_size,
-                                       enable_recv_pipe=args.enable_recv_pipe)
+                                       enable_recv_pipe=args.enable_recv_pipe,
+                                       enable_zerocopy_send=args.enable_zerocopy_send)
 
     p = subparsers.add_parser('sock_impl_set_options', help="""Set options of socket layer implementation""")
     p.add_argument('-i', '--impl', help='Socket implementation name, e.g. posix', required=True)
@@ -2408,7 +2409,11 @@ Format: 'user:u1 secret:s1 muser:mu1 msecret:ms1,user:u2 secret:s2 muser:mu2 mse
                    action='store_true', dest='enable_recv_pipe')
     p.add_argument('--disable-recv-pipe', help='Disable receive pipe',
                    action='store_false', dest='enable_recv_pipe')
-    p.set_defaults(func=sock_impl_set_options, enable_recv_pipe=None)
+    p.add_argument('--enable-zerocopy-send', help='Enable zerocopy on send',
+                   action='store_true', dest='enable_zerocopy_send')
+    p.add_argument('--disable-zerocopy-send', help='Disable zerocopy on send',
+                   action='store_false', dest='enable_zerocopy_send')
+    p.set_defaults(func=sock_impl_set_options, enable_recv_pipe=None, enable_zerocopy_send=None)
 
     def check_called_name(name):
         if name in deprecated_aliases:

scripts/rpc/sock.py

@@ -15,7 +15,8 @@ def sock_impl_set_options(client,
                           impl_name=None,
                           recv_buf_size=None,
                           send_buf_size=None,
-                          enable_recv_pipe=None):
+                          enable_recv_pipe=None,
+                          enable_zerocopy_send=None):
     """Set parameters for the socket layer implementation.
 
     Args:
@@ -23,6 +24,7 @@ def sock_impl_set_options(client,
         recv_buf_size: size of socket receive buffer in bytes (optional)
         send_buf_size: size of socket send buffer in bytes (optional)
         enable_recv_pipe: enable or disable receive pipe (optional)
+        enable_zerocopy_send: enable or disable zerocopy on send (optional)
     """
     params = {}
 
@@ -33,5 +35,7 @@ def sock_impl_set_options(client,
         params['send_buf_size'] = send_buf_size
     if enable_recv_pipe is not None:
         params['enable_recv_pipe'] = enable_recv_pipe
+    if enable_zerocopy_send is not None:
+        params['enable_zerocopy_send'] = enable_zerocopy_send
 
     return client.call('sock_impl_set_options', params)