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Commit 2d6491a5 authored by Chuck Lever's avatar Chuck Lever Committed by J. Bruce Fields
Browse files

svcrdma: Don't account for Receive queue "starvation" 



>From what I can tell, calling ->recvfrom when there is no work to do
is a normal part of operation. This is the only way svc_recv can
tell when there is no more data ready to receive on the transport.

Neither the TCP nor the UDP transport implementations have a
"starve" metric.

The cost of receive starvation accounting is bumping an atomic, which
results in extra (IMO unnecessary) bus traffic between CPU sockets,
while holding a spin lock.

Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent ca5c76ab

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

+6 −15
Original line number Diff line number Diff line
@@ -844,9 +844,9 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp) 
	struct svc_xprt *xprt = rqstp->rq_xprt;

	struct svcxprt_rdma *rdma_xprt =

		container_of(xprt, struct svcxprt_rdma, sc_xprt);

	struct svc_rdma_op_ctxt *ctxt = NULL;

	struct svc_rdma_op_ctxt *ctxt;

	struct rpcrdma_msg *rmsgp;

	int ret = 0;

	int ret;



	dprintk("svcrdma: rqstp=%p\n", rqstp);
@@ -863,21 +863,13 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp) 
					struct svc_rdma_op_ctxt, list);

		list_del(&ctxt->list);

	} else {

		atomic_inc(&rdma_stat_rq_starve);

		/* No new incoming requests, terminate the loop */

		clear_bit(XPT_DATA, &xprt->xpt_flags);

		ctxt = NULL;

	}

		spin_unlock(&rdma_xprt->sc_rq_dto_lock);

	if (!ctxt) {

		/* This is the EAGAIN path. The svc_recv routine will

		 * return -EAGAIN, the nfsd thread will go to call into

		 * svc_recv again and we shouldn't be on the active

		 * transport list

		 */

		if (test_bit(XPT_CLOSE, &xprt->xpt_flags))

			goto defer;

		goto out;

		return 0;

	}

	spin_unlock(&rdma_xprt->sc_rq_dto_lock);



	dprintk("svcrdma: processing ctxt=%p on xprt=%p, rqstp=%p\n",

		ctxt, rdma_xprt, rqstp);

	atomic_inc(&rdma_stat_recv);
@@ -920,7 +912,6 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp) 
		+ rqstp->rq_arg.page_len

		+ rqstp->rq_arg.tail[0].iov_len;

	svc_rdma_put_context(ctxt, 0);

 out:

	dprintk("svcrdma: ret=%d, rq_arg.len=%u, "

		"rq_arg.head[0].iov_base=%p, rq_arg.head[0].iov_len=%zd\n",

		ret, rqstp->rq_arg.len,