SUNRPC: Add a server side per-connection limit
Allow the user to limit the number of requests serviced through a single
connection, to help prevent faster clients from starving slower clients.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 82b42c9..48ba6d2 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3832,6 +3832,12 @@
using these two parameters to set the minimum and
maximum port values.
+ sunrpc.svc_rpc_per_connection_limit=
+ [NFS,SUNRPC]
+ Limit the number of requests that the server will
+ process in parallel from a single connection.
+ The default value is 0 (no limit).
+
sunrpc.pool_mode=
[NFS]
Control how the NFS server code allocates CPUs to
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 7ca44fb..7321ae9 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -268,6 +268,7 @@
* cache pages */
#define RQ_VICTIM (5) /* about to be shut down */
#define RQ_BUSY (6) /* request is busy */
+#define RQ_DATA (7) /* request has data */
unsigned long rq_flags; /* flags field */
void * rq_argp; /* decoded arguments */
diff --git a/include/linux/sunrpc/svc_xprt.h b/include/linux/sunrpc/svc_xprt.h
index 79ba508..ad899ff 100644
--- a/include/linux/sunrpc/svc_xprt.h
+++ b/include/linux/sunrpc/svc_xprt.h
@@ -69,6 +69,7 @@
struct svc_serv *xpt_server; /* service for transport */
atomic_t xpt_reserved; /* space on outq that is rsvd */
+ atomic_t xpt_nr_rqsts; /* Number of requests */
struct mutex xpt_mutex; /* to serialize sending data */
spinlock_t xpt_lock; /* protects sk_deferred
* and xpt_auth_cache */
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index e7082a4..2adc8db 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -21,6 +21,10 @@
#define RPCDBG_FACILITY RPCDBG_SVCXPRT
+static unsigned int svc_rpc_per_connection_limit __read_mostly;
+module_param(svc_rpc_per_connection_limit, uint, 0644);
+
+
static struct svc_deferred_req *svc_deferred_dequeue(struct svc_xprt *xprt);
static int svc_deferred_recv(struct svc_rqst *rqstp);
static struct cache_deferred_req *svc_defer(struct cache_req *req);
@@ -329,12 +333,41 @@
}
EXPORT_SYMBOL_GPL(svc_print_addr);
+static bool svc_xprt_slots_in_range(struct svc_xprt *xprt)
+{
+ unsigned int limit = svc_rpc_per_connection_limit;
+ int nrqsts = atomic_read(&xprt->xpt_nr_rqsts);
+
+ return limit == 0 || (nrqsts >= 0 && nrqsts < limit);
+}
+
+static bool svc_xprt_reserve_slot(struct svc_rqst *rqstp, struct svc_xprt *xprt)
+{
+ if (!test_bit(RQ_DATA, &rqstp->rq_flags)) {
+ if (!svc_xprt_slots_in_range(xprt))
+ return false;
+ atomic_inc(&xprt->xpt_nr_rqsts);
+ set_bit(RQ_DATA, &rqstp->rq_flags);
+ }
+ return true;
+}
+
+static void svc_xprt_release_slot(struct svc_rqst *rqstp)
+{
+ struct svc_xprt *xprt = rqstp->rq_xprt;
+ if (test_and_clear_bit(RQ_DATA, &rqstp->rq_flags)) {
+ atomic_dec(&xprt->xpt_nr_rqsts);
+ svc_xprt_enqueue(xprt);
+ }
+}
+
static bool svc_xprt_has_something_to_do(struct svc_xprt *xprt)
{
if (xprt->xpt_flags & ((1<<XPT_CONN)|(1<<XPT_CLOSE)))
return true;
if (xprt->xpt_flags & ((1<<XPT_DATA)|(1<<XPT_DEFERRED))) {
- if (xprt->xpt_ops->xpo_has_wspace(xprt))
+ if (xprt->xpt_ops->xpo_has_wspace(xprt) &&
+ svc_xprt_slots_in_range(xprt))
return true;
trace_svc_xprt_no_write_space(xprt);
return false;
@@ -516,8 +549,8 @@
rqstp->rq_res.head[0].iov_len = 0;
svc_reserve(rqstp, 0);
+ svc_xprt_release_slot(rqstp);
rqstp->rq_xprt = NULL;
-
svc_xprt_put(xprt);
}
@@ -785,7 +818,7 @@
svc_add_new_temp_xprt(serv, newxpt);
else
module_put(xprt->xpt_class->xcl_owner);
- } else {
+ } else if (svc_xprt_reserve_slot(rqstp, xprt)) {
/* XPT_DATA|XPT_DEFERRED case: */
dprintk("svc: server %p, pool %u, transport %p, inuse=%d\n",
rqstp, rqstp->rq_pool->sp_id, xprt,