| From cf002bbdab73a1193931266927c9d0f42c4a1086 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Wed, 8 Jul 2020 16:09:53 -0400 |
| Subject: SUNRPC: Mitigate cond_resched() in xprt_transmit() |
| |
| 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) { |
| -- |
| 2.27.0 |
| |
