From: Chuck Lever <chuck.lever@oracle.com>
Date: Wed, 8 Jul 2020 20:09:53 +0000 (-0400)
Subject: SUNRPC: Mitigate cond_resched() in xprt_transmit()
X-Git-Tag: v5.10.7~1364^2~42
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=6f9f17287e78e5049931af2037b15b26d134a32a;p=platform%2Fkernel%2Flinux-rpi.git

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) {