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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>
This commit is contained in:
Chuck Lever 2020-07-08 16:09:53 -04:00 committed by Anna Schumaker
parent db0a86c426
commit 6f9f17287e
1 changed files with 4 additions and 2 deletions
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6
net/sunrpc/xprt.c
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@ -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) {