Commit 6f9f1728 authored by Chuck Lever's avatar Chuck Lever Committed by Anna Schumaker
Browse files

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: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent db0a86c4

net/sunrpc/xprt.c

+4 −2
Original line number Diff line number Diff line
@@ -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) {