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Subject[PATCH AUTOSEL 5.9 079/147] SUNRPC: Mitigate cond_resched() in xprt_transmit()
Date
From: Chuck Lever <chuck.lever@oracle.com>

[ Upstream commit 6f9f17287e78e5049931af2037b15b26d134a32a ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sunrpc/xprt.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 5a8e47bbfb9f4..13fbc2dd4196a 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1520,10 +1520,13 @@ 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);
@@ -1531,7 +1534,6 @@ 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) {
--
2.25.1
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