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: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
include/linux/sunrpc/xprtsock.h | 2 ++
net/sunrpc/xprtsock.c | 51 +++++++++++++++++++++++++++++------------
2 files changed, 38 insertions(+), 15 deletions(-)
diff --git a/include/linux/sunrpc/xprtsock.h b/include/linux/sunrpc/xprtsock.h
index 357e44c1a46b..0ece4ba06f06 100644
--- a/include/linux/sunrpc/xprtsock.h
+++ b/include/linux/sunrpc/xprtsock.h
@@ -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;
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index fa8d0c15c8cd..58dc90ccebb6 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -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:
--
2.4.3
--
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