SUNRPC: Mitigate cond_resched() in xprt_transmit()
The original purpose of this expensive call is to prevent a long
queue of requests from blocking other work.
The cond_resched() call is unnecessary after just a single send
operation.
For longer queues, instead of invoking the kernel scheduler, simply
release the transport send lock and return to the RPC scheduler.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index ceb190d..f6c17e7 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1513,10 +1513,13 @@ xprt_transmit(struct rpc_task *task)
{
struct rpc_rqst *next, *req = task->tk_rqstp;
struct rpc_xprt *xprt = req->rq_xprt;
- int status;
+ int counter, status;
spin_lock(&xprt->queue_lock);
+ counter = 0;
while (!list_empty(&xprt->xmit_queue)) {
+ if (++counter == 20)
+ break;
next = list_first_entry(&xprt->xmit_queue,
struct rpc_rqst, rq_xmit);
xprt_pin_rqst(next);
@@ -1524,7 +1527,6 @@ xprt_transmit(struct rpc_task *task)
status = xprt_request_transmit(next, task);
if (status == -EBADMSG && next != req)
status = 0;
- cond_resched();
spin_lock(&xprt->queue_lock);
xprt_unpin_rqst(next);
if (status == 0) {