This is a note to let you know that I've just added the patch titled
SUNRPC: Mitigate cond_resched() in xprt_transmit()
to the 5.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sunrpc-mitigate-cond_resched-in-xprt_transmit.patch
and it can be found in the queue-5.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit cf002bbdab73a1193931266927c9d0f42c4a1086
Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
Date: Wed Jul 8 16:09:53 2020 -0400
SUNRPC: Mitigate cond_resched() in xprt_transmit()
[ 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@xxxxxxxxxx>
Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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) {
