Commit edc1b01c authored by Trond Myklebust's avatar Trond Myklebust
Browse files

SUNRPC: Move TCP receive data path into a workqueue context 



Stream protocols such as TCP can often build up a backlog of data to be
read due to ordering. Combine this with the fact that some workloads such
as NFS read()-intensive workloads need to receive a lot of data per RPC
call, and it turns out that receiving the data from inside a softirq
context can cause starvation.

The following patch moves the TCP data receive into a workqueue context.
We still end up calling tcp_read_sock(), but we do so from a process
context, meaning that softirqs are enabled for most of the time.

With this patch, I see a doubling of read bandwidth when running a
multi-threaded iozone workload between a virtual client and server setup.

Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent 66d7a56a

include/linux/sunrpc/xprtsock.h

+2 −0
Original line number Diff line number Diff line
@@ -44,6 +44,8 @@ struct sock_xprt { 
	 */

	unsigned long		sock_state;

	struct delayed_work	connect_worker;

	struct work_struct	recv_worker;

	struct mutex		recv_mutex;

	struct sockaddr_storage	srcaddr;

	unsigned short		srcport;

net/sunrpc/xprtsock.c

+36 −15
Original line number Diff line number Diff line
@@ -823,6 +823,7 @@ static void xs_reset_transport(struct sock_xprt *transport) 


	kernel_sock_shutdown(sock, SHUT_RDWR);



	mutex_lock(&transport->recv_mutex);

	write_lock_bh(&sk->sk_callback_lock);

	transport->inet = NULL;

	transport->sock = NULL;
@@ -833,6 +834,7 @@ static void xs_reset_transport(struct sock_xprt *transport) 
	xprt_clear_connected(xprt);

	write_unlock_bh(&sk->sk_callback_lock);

	xs_sock_reset_connection_flags(xprt);

	mutex_unlock(&transport->recv_mutex);



	trace_rpc_socket_close(xprt, sock);

	sock_release(sock);
@@ -886,6 +888,7 @@ static void xs_destroy(struct rpc_xprt *xprt) 


	cancel_delayed_work_sync(&transport->connect_worker);

	xs_close(xprt);

	cancel_work_sync(&transport->recv_worker);

	xs_xprt_free(xprt);

	module_put(THIS_MODULE);

}
@@ -1243,12 +1246,12 @@ static inline int xs_tcp_read_reply(struct rpc_xprt *xprt, 
	dprintk("RPC:       read reply XID %08x\n", ntohl(transport->tcp_xid));



	/* Find and lock the request corresponding to this xid */

	spin_lock(&xprt->transport_lock);

	spin_lock_bh(&xprt->transport_lock);

	req = xprt_lookup_rqst(xprt, transport->tcp_xid);

	if (!req) {

		dprintk("RPC:       XID %08x request not found!\n",

				ntohl(transport->tcp_xid));

		spin_unlock(&xprt->transport_lock);

		spin_unlock_bh(&xprt->transport_lock);

		return -1;

	}
@@ -1257,7 +1260,7 @@ static inline int xs_tcp_read_reply(struct rpc_xprt *xprt, 
	if (!(transport->tcp_flags & TCP_RCV_COPY_DATA))

		xprt_complete_rqst(req->rq_task, transport->tcp_copied);



	spin_unlock(&xprt->transport_lock);

	spin_unlock_bh(&xprt->transport_lock);

	return 0;

}
@@ -1277,10 +1280,10 @@ static int xs_tcp_read_callback(struct rpc_xprt *xprt, 
	struct rpc_rqst *req;



	/* Look up and lock the request corresponding to the given XID */

	spin_lock(&xprt->transport_lock);

	spin_lock_bh(&xprt->transport_lock);

	req = xprt_lookup_bc_request(xprt, transport->tcp_xid);

	if (req == NULL) {

		spin_unlock(&xprt->transport_lock);

		spin_unlock_bh(&xprt->transport_lock);

		printk(KERN_WARNING "Callback slot table overflowed\n");

		xprt_force_disconnect(xprt);

		return -1;
@@ -1291,7 +1294,7 @@ static int xs_tcp_read_callback(struct rpc_xprt *xprt, 


	if (!(transport->tcp_flags & TCP_RCV_COPY_DATA))

		xprt_complete_bc_request(req, transport->tcp_copied);

	spin_unlock(&xprt->transport_lock);

	spin_unlock_bh(&xprt->transport_lock);



	return 0;

}
@@ -1402,19 +1405,33 @@ static void xs_tcp_data_receive(struct sock_xprt *transport) 
	unsigned long total = 0;

	int read = 0;



	mutex_lock(&transport->recv_mutex);

	sk = transport->inet;

	if (sk == NULL)

		goto out;



	/* We use rd_desc to pass struct xprt to xs_tcp_data_recv */

	for (;;) {

		lock_sock(sk);

		read = tcp_read_sock(sk, &rd_desc, xs_tcp_data_recv);

		release_sock(sk);

		if (read <= 0)

			break;

		total += read;

		rd_desc.count = 65536;

	}

out:

	mutex_unlock(&transport->recv_mutex);

	trace_xs_tcp_data_ready(xprt, read, total);

}



static void xs_tcp_data_receive_workfn(struct work_struct *work)

{

	struct sock_xprt *transport =

		container_of(work, struct sock_xprt, recv_worker);

	xs_tcp_data_receive(transport);

}



/**

 * xs_tcp_data_ready - "data ready" callback for TCP sockets

 * @sk: socket with data to read
@@ -1437,8 +1454,8 @@ static void xs_tcp_data_ready(struct sock *sk) 
	 */

	if (xprt->reestablish_timeout)

		xprt->reestablish_timeout = 0;

	queue_work(rpciod_workqueue, &transport->recv_worker);



	xs_tcp_data_receive(transport);

out:

	read_unlock_bh(&sk->sk_callback_lock);

}
@@ -1840,6 +1857,10 @@ static inline void xs_reclassify_socket(int family, struct socket *sock) 
}

#endif



static void xs_dummy_data_receive_workfn(struct work_struct *work)

{

}



static void xs_dummy_setup_socket(struct work_struct *work)

{

}
@@ -2664,6 +2685,7 @@ static struct rpc_xprt *xs_setup_xprt(struct xprt_create *args, 
	}



	new = container_of(xprt, struct sock_xprt, xprt);

	mutex_init(&new->recv_mutex);

	memcpy(&xprt->addr, args->dstaddr, args->addrlen);

	xprt->addrlen = args->addrlen;

	if (args->srcaddr)
@@ -2717,6 +2739,7 @@ static struct rpc_xprt *xs_setup_local(struct xprt_create *args) 
	xprt->ops = &xs_local_ops;

	xprt->timeout = &xs_local_default_timeout;



	INIT_WORK(&transport->recv_worker, xs_dummy_data_receive_workfn);

	INIT_DELAYED_WORK(&transport->connect_worker,

			xs_dummy_setup_socket);
@@ -2788,21 +2811,20 @@ static struct rpc_xprt *xs_setup_udp(struct xprt_create *args) 


	xprt->timeout = &xs_udp_default_timeout;



	INIT_WORK(&transport->recv_worker, xs_dummy_data_receive_workfn);

	INIT_DELAYED_WORK(&transport->connect_worker, xs_udp_setup_socket);



	switch (addr->sa_family) {

	case AF_INET:

		if (((struct sockaddr_in *)addr)->sin_port != htons(0))

			xprt_set_bound(xprt);



		INIT_DELAYED_WORK(&transport->connect_worker,

					xs_udp_setup_socket);

		xs_format_peer_addresses(xprt, "udp", RPCBIND_NETID_UDP);

		break;

	case AF_INET6:

		if (((struct sockaddr_in6 *)addr)->sin6_port != htons(0))

			xprt_set_bound(xprt);



		INIT_DELAYED_WORK(&transport->connect_worker,

					xs_udp_setup_socket);

		xs_format_peer_addresses(xprt, "udp", RPCBIND_NETID_UDP6);

		break;

	default:
@@ -2867,21 +2889,20 @@ static struct rpc_xprt *xs_setup_tcp(struct xprt_create *args) 
	xprt->ops = &xs_tcp_ops;

	xprt->timeout = &xs_tcp_default_timeout;



	INIT_WORK(&transport->recv_worker, xs_tcp_data_receive_workfn);

	INIT_DELAYED_WORK(&transport->connect_worker, xs_tcp_setup_socket);



	switch (addr->sa_family) {

	case AF_INET:

		if (((struct sockaddr_in *)addr)->sin_port != htons(0))

			xprt_set_bound(xprt);



		INIT_DELAYED_WORK(&transport->connect_worker,

					xs_tcp_setup_socket);

		xs_format_peer_addresses(xprt, "tcp", RPCBIND_NETID_TCP);

		break;

	case AF_INET6:

		if (((struct sockaddr_in6 *)addr)->sin6_port != htons(0))

			xprt_set_bound(xprt);



		INIT_DELAYED_WORK(&transport->connect_worker,

					xs_tcp_setup_socket);

		xs_format_peer_addresses(xprt, "tcp", RPCBIND_NETID_TCP6);

		break;

	default:

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