[dpdk-dev] [PATCH 5/6] vhost: add a flag to enable Tx zero copy

Xu, Qian Q qian.q.xu at intel.com
Tue Sep 6 11:00:14 CEST 2016


Just curious about the naming: vhost USER TX Zero copy. In fact, it's Vhost RX zero-copy
For virtio, it's Virtio TX zero-copy. So, I wonder why we call it as Vhost TX ZERO-COPY, 
Any comments? 

-----Original Message-----
From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Yuanhan Liu
Sent: Tuesday, August 23, 2016 4:11 PM
To: dev at dpdk.org
Cc: Maxime Coquelin; Yuanhan Liu
Subject: [dpdk-dev] [PATCH 5/6] vhost: add a flag to enable Tx zero copy

Add a new flag ``RTE_VHOST_USER_TX_ZERO_COPY`` to explictily enable
Tx zero copy. If not given, Tx zero copy is disabled by default.

Signed-off-by: Yuanhan Liu <yuanhan.liu at linux.intel.com>
---
 doc/guides/prog_guide/vhost_lib.rst |  7 ++++++-
 lib/librte_vhost/rte_virtio_net.h   |  1 +
 lib/librte_vhost/socket.c           |  5 +++++
 lib/librte_vhost/vhost.c            | 10 ++++++++++
 lib/librte_vhost/vhost.h            |  1 +
 5 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst
index 6b0c6b2..15c2bf7 100644
--- a/doc/guides/prog_guide/vhost_lib.rst
+++ b/doc/guides/prog_guide/vhost_lib.rst
@@ -79,7 +79,7 @@ The following is an overview of the Vhost API functions:
   ``/dev/path`` character device file will be created. For vhost-user server
   mode, a Unix domain socket file ``path`` will be created.
 
-  Currently two flags are supported (these are valid for vhost-user only):
+  Currently supported flags are (these are valid for vhost-user only):
 
   - ``RTE_VHOST_USER_CLIENT``
 
@@ -97,6 +97,11 @@ The following is an overview of the Vhost API functions:
     This reconnect option is enabled by default. However, it can be turned off
     by setting this flag.
 
+  - ``RTE_VHOST_USER_TX_ZERO_COPY``
+
+    Tx zero copy will be enabled when this flag is set. It is disabled by
+    default.
+
 * ``rte_vhost_driver_session_start()``
 
   This function starts the vhost session loop to handle vhost messages. It
diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
index 9caa622..5e437c6 100644
--- a/lib/librte_vhost/rte_virtio_net.h
+++ b/lib/librte_vhost/rte_virtio_net.h
@@ -53,6 +53,7 @@
 
 #define RTE_VHOST_USER_CLIENT		(1ULL << 0)
 #define RTE_VHOST_USER_NO_RECONNECT	(1ULL << 1)
+#define RTE_VHOST_USER_TX_ZERO_COPY	(1ULL << 2)
 
 /* Enum for virtqueue management. */
 enum {VIRTIO_RXQ, VIRTIO_TXQ, VIRTIO_QNUM};
diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
index bf03f84..5c3962d 100644
--- a/lib/librte_vhost/socket.c
+++ b/lib/librte_vhost/socket.c
@@ -62,6 +62,7 @@ struct vhost_user_socket {
 	int connfd;
 	bool is_server;
 	bool reconnect;
+	bool tx_zero_copy;
 };
 
 struct vhost_user_connection {
@@ -203,6 +204,9 @@ vhost_user_add_connection(int fd, struct vhost_user_socket *vsocket)
 	size = strnlen(vsocket->path, PATH_MAX);
 	vhost_set_ifname(vid, vsocket->path, size);
 
+	if (vsocket->tx_zero_copy)
+		vhost_enable_tx_zero_copy(vid);
+
 	RTE_LOG(INFO, VHOST_CONFIG, "new device, handle is %d\n", vid);
 
 	vsocket->connfd = fd;
@@ -499,6 +503,7 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
 	memset(vsocket, 0, sizeof(struct vhost_user_socket));
 	vsocket->path = strdup(path);
 	vsocket->connfd = -1;
+	vsocket->tx_zero_copy = flags & RTE_VHOST_USER_TX_ZERO_COPY;
 
 	if ((flags & RTE_VHOST_USER_CLIENT) != 0) {
 		vsocket->reconnect = !(flags & RTE_VHOST_USER_NO_RECONNECT);
diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index ab25649..5461e5b 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -290,6 +290,16 @@ vhost_set_ifname(int vid, const char *if_name, unsigned int if_len)
 	dev->ifname[sizeof(dev->ifname) - 1] = '\0';
 }
 
+void
+vhost_enable_tx_zero_copy(int vid)
+{
+	struct virtio_net *dev = get_device(vid);
+
+	if (dev == NULL)
+		return;
+
+	dev->tx_zero_copy = 1;
+}
 
 int
 rte_vhost_get_numa_node(int vid)
diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 718133e..3081180 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -279,6 +279,7 @@ void vhost_destroy_device(int);
 int alloc_vring_queue_pair(struct virtio_net *dev, uint32_t qp_idx);
 
 void vhost_set_ifname(int, const char *if_name, unsigned int if_len);
+void vhost_enable_tx_zero_copy(int vid);
 
 /*
  * Backend-specific cleanup. Defined by vhost-cuse and vhost-user.
-- 
1.9.0



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